Billing and keys

Everything a developer needs to call paid APIs on API Mercado: how to authenticate, what each call costs, how balances, holds and spend caps work, and how to read every error the gateway can return.

Authenticating requests

Every request carries a Key in the X-API-Key header:

curl -H "X-API-Key: mk_live_…" "https://eu-north-1.apimercado.com/v1/@<provider-slug>/<api-slug>/<path>"

Get a Key from any API’s page: enable the API, then press Create key in the dialog that follows. The Keys page lists every Key and mints ones scoped to several APIs or capped per Month.

Keys are shown once at creation. Keep them server-side; a leaked Key spends your balance. Revoke and re-create from the Keys page. There is no rotation window and no expiry.

Keyless operations

A few operations need no Key: those an API’s provider made keyless (marked security: [] in its published spec), and every API’s health check path. They are free and not metered, so a browser can call them directly, and the gateway allows 60 of them per minute per IP address and API (keyless_rate_limited beyond that). A Key sent to one is removed and ignored, and the provider does not see who called.

Test requests from an API page

An org admin can send a test request from any API page their organization has enabled (“Try it”). The marketplace sends it through the gateway with your organization’s Portal test key, which it creates on the first test and lists on the Keys page. A test request is billed exactly like any other call, from the same balance, and shows up in your requests and spend. You can give the Portal test key a Spend cap or revoke it; the next test creates a new one. Test requests are limited to 10 per minute per organization.

TypeScript client

@apimercado/client wraps openapi-fetch with the gateway URL, the Key header and the gateway error shape. Every API page shows the one-liner that generates its types; it fetches the API’s OpenAPI spec from the gateway and writes a .d.ts file you commit:

npm install @apimercado/client
npx @apimercado/client generate @<provider-slug>/<api-slug> -o <api-slug>.d.ts

import { createApimercadoClient } from "@apimercado/client";
import type { paths } from "./<api-slug>";

const api = createApimercadoClient<paths>({
  provider: "@<provider-slug>",
  api: "<api-slug>",
  apiKey: "mk_live_...",
});
const { data, error } = await api.GET("/<path>", { params: { query: { ... } } });

Providers can publish new versions and the gateway always serves the current one. The generated file records the spec hash it was built from, so npx @apimercado/client check <api-slug>.d.ts exits 1 in CI when the spec changed; regenerate and let the compiler point at the calls that no longer match.

The client also sets Max cost for you (maxCostMicros), reads every response header (readCost), and types the balance endpoint and the request lookup (createAccountClient).

Base URL shape

All API traffic goes through the marketplace gateway:

https://eu-north-1.apimercado.com/v1/@<provider-slug>/<api-slug>/…

@<provider-slug> is the provider organization’s slug, the same name as in the marketplace URL https://apimercado.com/discover/<provider-slug>/<api-slug>. The provider’s public id (shown in small print at the bottom of every API page) works in its place, /v1/<provider-public-id>/<api-slug>/…, so URLs copied before slugs existed keep working. Every API page also has a markdown twin at <page>/llms.txt with this whole setup written for a coding agent.

The same gateway hosts two platform endpoints under the reserved public id account:

GET https://eu-north-1.apimercado.com/v1/account/balance
GET https://eu-north-1.apimercado.com/v1/account/requests/{requestId}

They are authenticated with any of your org’s Keys, exactly like an API call, and are never charged.

The balance endpoint

GET /v1/account/balance returns your organization’s current billing state. All money fields are integer micro-dollars (1,000,000 = $1.00) with the unit in the field name:

{
  "monthly_balance_micros": 412000,
  "topup_balance_micros": 12500000,
  "available_balance_micros": 12912000,
  "month_resets_at": "2026-10-01T00:00:00.000Z",
  "key_spend_micros": 750000,
  "key_spend_cap_micros": 5000000,
  "next_expiring_lot": {
    "amount_micros": 12500000,
    "expires_at": "2028-03-01T00:00:00.000Z"
  }
}

• monthly_balance_micros: what remains of this Month’s Free buffer.
• topup_balance_micros: what remains of your purchased Top-up balance.
• available_balance_micros: the two combined; a request is denied when it would cost more than this.
• month_resets_at: when the Monthly balance resets (the 1st of next Month, UTC).
• key_spend_micros: what the calling Key has spent this Month.
• key_spend_cap_micros: the calling Key’s Spend cap, or null when unlimited.
• next_expiring_lot: the soonest-expiring Top-up Lot with its remaining amount, or null when nothing is left to expire.

Response headers

Header	On	Value
X-Mercado-Request-Id	every response to an API call, including the gateway’s 400, 402, 403, 429 and 503 denials	The request’s id. Use it for the request lookup and in support questions.
X-Mercado-Cost-Micros	every served response	The Cost of that request, so far. On a call to your own API it is the full Cost, though only the proxy fee was deducted.
X-Mercado-Fee-Micros	every served response	The proxy fee part of that Cost.
X-Mercado-Charge	calls to an API your own organization publishes	internal: the call is priced in full, but only the proxy fee is deducted.
X-Mercado-Balance-Micros	every served response	Your Available balance after what was deducted.
X-Mercado-Resets-At	every served response	When the Monthly balance resets.
X-Mercado-Settlement	operations settled later	pending: the price comes later (see Holds). instant: charged in full now.
X-Mercado-Hold-Micros	with X-Mercado-Settlement: pending	What is held until the provider settles.

The only response without X-Mercado-Request-Id is the gateway’s static 403 for an unknown or revoked Key (see api_not_enabled). A rate-limited request returns 429 with a Retry-After header. The TypeScript client reads all of them with readCost(response).

What is charged

You pay the request’s Cost: the API’s Price plus a fixed proxy fee per request. Every price on the Marketplace is the provider’s Price alone, marked ”+ proxy fee”, so an API with a $0 Price shows as Free; the enable dialog spells the fee out. Providers may vary the Price per request up to the price cap shown on the API page, so check X-Mercado-Cost-Micros rather than assuming a list Price. Calls to an API your own organization publishes are priced like any other call, but only the proxy fee is deducted: their response headers report the full Cost and carry X-Mercado-Charge: internal. To bound what a single call may cost, see Max cost. Topping up costs a separate percentage fee, added on top of the amount you buy and shown on your Stripe invoice.

The current figures (the proxy fee, the top-up fee, the Free buffer, the smallest top-up and how long purchased dollars last) are on the fees overview. Signed in, your organization’s own figures are on its Billing page.

A request is charged when the upstream API answers with a 2xx or 4xx status, except 401, 403, and 429: those mean the provider’s upstream rejected or throttled the gateway itself, so you are not charged for them. Upstream 5xx responses, timeouts, and every gateway denial are never charged.

Your Key never leaves the gateway. The X-API-Key header is removed before the request is forwarded, and the provider identifies you only by the X-Mercado-Consumer-Id and X-Mercado-Key-Id headers. APIs with a $0 Price still require a Key and Access, and are rate-limited and logged. They earn the Provider nothing, and cost you only the per-request proxy fee.

Prices and price changes

An API page shows what its requests actually cost: the 5th to 95th percentile of the charged Price over the last 30 days, refreshed every 5 minutes, for example “$0.0004 to $0.0012 per request, up to $0.002”. Until an API has 20 charged requests in that window it shows “Up to $0.002 per request”. The cap, the most one request can cost, is always shown. Operations with their own pricing show their own range and cap in the endpoint list.

When a provider raises a price or a cap, every organization with the API enabled gets an email, and the API page shows “Price raised on ” or “Price cap raised on ” for 30 days. A provider turning off the Free buffer for its API emails you too. Lowerings send nothing.

Some APIs need a Top-up balance: their page says so. Your Free buffer pays only the proxy fee on them, so their free operations keep working without a top-up (see topup_required).

An operation marked “Not available yet” is priced by a provider that cannot charge for calls yet. Calls to it are refused with paid_pricing_unavailable and cost nothing; the API’s free operations work as usual.

Max cost

To bound what one call may cost you, proxy fee included, send X-Mercado-Max-Cost-Micros with the request:

curl -H "X-API-Key: mk_live_…" -H "X-Mercado-Max-Cost-Micros: 20000" "https://eu-north-1.apimercado.com/v1/@<provider-slug>/<api-slug>/<path>"

• The gateway compares it with the most the call can cost: the called operation’s price cap plus the proxy fee. When that is above your value, the call is refused with 402 max_cost_exceeded before the provider is called, and nothing is held or charged. Set it against the cap shown on the API page, not against what calls usually cost.
• An allowed call reaches the provider with the header unchanged, so it can scale the work to your Max cost. You are still charged at most the operation’s cap plus the proxy fee.
• The value is a whole number of micro-dollars, digits only. Anything else (a sign, a decimal point, spaces, an empty value, a number too large for a 64-bit integer) is ignored and not forwarded, as if you had sent none.
• It applies to calls to your own organization’s APIs too, checked against the full Cost. Keyless operations ignore it and do not forward it.

The TypeScript client sends it on every call when created with maxCostMicros.

Balances: Free buffer and Month reset

Spend draws from two pools, Monthly first:

1. Monthly balance: the Free buffer every organization gets each Month (see What is charged for the amount). It is a trial the Marketplace funds, so Spend from it earns the Provider nothing. What you do not spend does not carry over: the balance resets on the 1st of each Month at 00:00 UTC.
2. Top-up balance: prepaid dollars you purchase. It never resets, and is spent only after the Monthly balance is exhausted.

Holds

Before a request reaches the provider, the gateway holds the most it can cost: the called operation’s price cap plus the proxy fee. Requests in flight at the same time cannot spend the same dollars, and a request is never half-paid. The hold ends when the response is charged, after at most 60 seconds.

Some operations are settled later: the provider only knows the price once the work is done (a video render, a transcript). The API’s spec declares them, and they work differently:

1. The gateway holds the operation’s cap from your Top-up balance, minus your other open holds. The Free buffer never funds this hold. Without enough Top-up the request is denied with topup_required before the provider is called.
2. The response carries X-Mercado-Settlement: pending and X-Mercado-Hold-Micros. You pay the proxy fee now (X-Mercado-Cost-Micros).
3. The provider settles the request once, for 0 up to the hold. You pay the settled amount from Top-up and the rest is released. A hold the provider never settles is released after 48 hours.

The proxy fee is not returned when a hold is released. Open holds count toward the Key’s Spend cap, and a settled amount counts toward the Month the request was made in. A provider may answer such a request with X-Mercado-Settlement: instant (a cached result, a rejected input): it is then charged in full at once, like any other request.

Example: an operation with a $0.25 cap. The submit holds 250000 micro-dollars and costs the proxy fee. The provider settles 182000: you pay $0.182 and the other $0.068 is released.

The request lookup

GET /v1/account/requests/{requestId} returns one request of your organization by its X-Mercado-Request-Id. It is free and authenticated with any of your org’s Keys:

curl -H "X-API-Key: mk_live_…" "https://eu-north-1.apimercado.com/v1/account/requests/4f1c2b9e-0d7a-4b8e-9a51-2f3c6d7e8a90"

{
  "request_id": "4f1c2b9e-0d7a-4b8e-9a51-2f3c6d7e8a90",
  "status": "pending",
  "price_micros": 0,
  "fee_micros": 100,
  "cost_micros": 100,
  "raw_cost_micros": 100,
  "hold_micros": 250000,
  "internal": false
}

The amounts in this example are illustrative; fee_micros is the proxy fee in force when the request was made.

status	Meaning
charged	Charged in full when the response came back.
pending	Settled later: the proxy fee is charged, hold_micros is held until the provider settles.
settled	The provider settled: price_micros is the settled amount, cost_micros adds the proxy fee.
released	The hold was released without a price (a $0 settle or 48 hours without one). Only the proxy fee was charged.
not_charged	Denied by the gateway or not charged (upstream 5xx, 401, 403 or 429). All amounts are 0.

• price_micros, fee_micros, cost_micros: what the request charged. On a call to an API your own organization publishes they are the full amounts, though only the proxy fee was deducted.
• raw_cost_micros: deprecated, always equal to cost_micros. Read cost_micros instead; this field will be removed.
• hold_micros: what is held now; 0 unless pending.
• internal: true on a call to an API your own organization publishes.

A request settled later is read from its hold record, and is final once settled or released. Any other request is read from the request log: it appears a few seconds after its response and is kept 90 days. A request id of another organization answers like an unknown one (request_not_found).

Spend caps

Each Key can carry an optional monthly Spend cap. When the Key’s own Spend this Month reaches its cap, only that Key is denied; your other Keys keep working until the org balance runs out. An unset cap means unlimited (bounded by the org balance).

Expiry

Top-up dollars arrive in Lots, and each Lot expires a fixed number of months after it lands (see What is charged for how many). Spend consumes the soonest-expiring Lot first, so nothing goes stale while a later Lot could be spent. The balance endpoint’s next_expiring_lot shows what expires next; expired amounts simply leave the Top-up balance.

Error codes

Gateway-generated errors share one body shape:

{
  "error": {
    "code": "balance_exhausted",
    "message": "The organization balance is exhausted.",
    "resets_at": "2026-10-01T00:00:00.000Z",
    "docs": "https://docs.apimercado.com/billing-and-keys/#balance_exhausted"
  }
}

resets_at is the next Month reset (the 1st of next Month, 00:00 UTC). Every denial the billing gateway generates carries it, even org_suspended, api_not_enabled, and billing_state_unavailable, which are not really about the Month reset, so a client can always say when the error state may change. It is null only on the gateway’s static 403 from its own key authentication (see api_not_enabled) and on the account endpoints’ own key_not_authorized and request_not_found. docs links to the anchor below.

key_not_authorized

401: returned only by the account endpoints themselves, when the caller identity the gateway forwarded does not check out: the request bypassed the gateway, or the Key’s platform metadata is stale. This is not what a revoked Key sees in normal use: the gateway rejects a revoked or unknown Key first, with api_not_enabled below.

request_not_found

404: the request lookup found no request with this id in your organization. The id may be mistyped, belong to another organization, or be older than 90 days. A request charged in full appears a few seconds after its response, so retry a just-made one shortly.

api_not_enabled

403: the Key has no Access to this API. Enable the API for your organization, or widen the Key’s Scope, and retry.

A revoked or unknown Key gets this same code: the gateway’s own authentication rejects it before any billing check runs, answering HTTP 403 with a static body whose resets_at is null. Revoked Keys are gone for good: mint a new Key on the Keys page.

org_suspended

403: the organization is suspended. All Keys are denied until the suspension is lifted; contact support.

balance_exhausted

402: the Available balance (Monthly plus Top-up, minus your open holds) cannot cover the most the request can cost, which is the called operation’s price cap plus the proxy fee. The check runs before the call reaches the provider, so a request is never half-paid. Top up, or wait for the Month reset in resets_at.

topup_required

402: the Price of this request must be paid from purchased dollars, and your Top-up balance (minus your open holds) cannot cover its price cap. This happens on an API whose provider asks for it (its page says calls need a topped-up balance) and on every operation settled later (see Holds). Your Free buffer still pays the proxy fee, so an API’s free operations keep working. Top up and retry.

key_spend_cap_reached

402: this Key reached its monthly Spend cap, or has too little room under it for the hold an operation settled later needs. Raise the cap, use another Key, or wait for the Month reset in resets_at.

max_cost_exceeded

402: the most this call can cost, the called operation’s price cap plus the proxy fee, is above the X-Mercado-Max-Cost-Micros you sent (see Max cost). The provider was not called, and nothing was held or charged. Raise the header, or leave it out, and retry.

paid_pricing_unavailable

503: the called operation is priced, and its provider cannot charge for calls yet (the API page marks it “Not available yet”). The provider was not called, and nothing was held or charged. The API’s operations without a price still work. Retrying the same operation gets the same answer until the provider can charge.

billing_state_unavailable

503: the billing system could not read your balance or the API’s pricing, so the gateway failed closed. Nothing was charged. Retry shortly.

path_not_routable

400: the gateway cannot tell which operation this path calls, so it cannot price it. This happens on APIs that price operations in their spec, when a path segment holds an encoded slash (%2F) or a backslash, or when the path is not under the API’s base URL. Nothing was charged, and retrying the same URL gets the same answer: fix the URL.

keyless_rate_limited

429: too many calls to an API’s keyless operations (see Keyless operations) from one IP address within a minute. Wait for the next minute and retry.

Disputes

Charged incorrectly? From your request log, an org admin can report any charged or settled request within 30 days of the request, with a description of what went wrong. A resolved refund returns the full Cost (for a settled request, the settled amount plus the proxy fee) to your Top-up balance and shows up in your balance history; the provider is deducted the Price portion and the platform forgoes its fee.

request_not_settled

A pending request cannot be disputed yet: it has no price. Report it once the provider settles it, or wait for its release.

request_released

A released request cannot be disputed: it charged only the proxy fee, which a release never returns, so there is nothing to refund.