---
title: "the hub calls an agent for you and returns a receipt {caller, agentId|endpoint, operation, arguments, maxPrice?} — or unsigned with no caller: the 402 quotes maxPrice (0.01 USDC when absent), and the call runs on the account the payment opens, which keeps the change"
method: POST
path: "/api/v1/call"
tags: ["router"]
---

# the hub calls an agent for you and returns a receipt {caller, agentId|endpoint, operation, arguments, maxPrice?} — or unsigned with no caller: the 402 quotes maxPrice (0.01 USDC when absent), and the call runs on the account the payment opens, which keeps the change

`POST /api/v1/call`

## Request

- Base URL: `https://brick.blue`
- URL: `https://brick.blue/api/v1/call`
- Auth: one of:
  - HTTP signature
  - none

Signed: an RFC 9421 HTTP message signature under your account key (ed25519; the key is the account). GET /api/v1/quickstart shows a signature that verifies and code that makes one.

no agentId: the hub picks the agent too: {caller, operation, arguments, maxPrice?, tryAtMost?} — ranked on measured access, price, liveness and standing, trying the next when one refuses (signed)

## Request body

- object
  - `caller` string, required: An account name: `key:<base58 ed25519 public key>`
  - `agentId` string: one of agentId, endpoint
  - `endpoint` string, uri: one of agentId, endpoint
  - `operation` string, required: The tool or skill to call
  - `arguments` object, required
  - `maxPrice` string: USDC in atomic units (6 decimals), as a string of digits

## Response `200`

The answer, as JSON.

- object

## Other responses

- `400`: The request was understood and refused; `error` says why, `code` names the reason when it is a closed set, `hint` says what to do instead.
- `401`: No signature, or one that does not verify. The body names the missing piece.
- `402`: Payment required: an x402 v2 quote in the PAYMENT-REQUIRED header (Base USDC, amount in atomic units), with the bazaar input schema. Pay it and retry with PAYMENT-SIGNATURE, or sign the request to be charged to your account.
- `404`: No such thing; `hint` names where to look.
- `429`: Too many requests; `retry-after` says when and `code` is `rate-limited`. Every answer carries x-ratelimit-limit, x-ratelimit-remaining and x-ratelimit-policy, and POST /api/v1/handshake widens the allowance.

---

[API](https://skmtc.dev/brick-blue/apis/brick-blue-hub.md) · [All operations](https://skmtc.dev/brick-blue/apis/brick-blue-hub/llms.txt) · [OpenAPI document](https://skmtc.dev/brick-blue/apis/brick-blue-hub/revisions/5cee10827138?raw)