---
title: "MCP endpoint (Streamable HTTP). One tool: fidren_check_counterparty."
method: POST
path: "/mcp"
tags: ["Discovery"]
---

# MCP endpoint (Streamable HTTP). One tool: fidren_check_counterparty.

`POST /mcp`

## Request

- Base URL: `https://api.fidren.net`
- URL: `https://api.fidren.net/mcp`
- Auth: one of:
  - none
  - HTTP bearer
  - API key in header `X-API-Key`

JSON-RPC over a single POST. Implements `tools/list` and `tools/call`, plus `initialize` for clients on protocol revisions before `2026-07-28`, which still require a handshake.

Responses are `application/json`; no stream is opened, because a decision is one round trip and there is nothing to stream.

Admission matches `/v1/decision`. A `402` carries the x402 terms.

`GET` and `DELETE` answer `405`: the standalone SSE stream and the session teardown are part of revisions this server does not implement.

## Request body

- object
  - `jsonrpc` '2.0', required
  - `id` unknown
  - `method` 'initialize' | 'notifications/initialized' | 'tools/list' | 'tools/call', required
  - `params` object

## Response `200`

A JSON-RPC result.

- object

## Other responses

- `202`: A notification was accepted. No body.
- `400`: Malformed JSON-RPC, or mirrored headers that disagree with the body (JSON-RPC error `-32020`).
- `401`: No usable access path. Either a key was presented and is not valid, or no key was presented, the free allowance is spent, and x402 charging is off. A presented key never falls back to the free tier or to being charged.
- `402`: Payment required. Carries the x402 terms.
- `403`: The API key is valid, but its organization is not currently permitted to make this request. Do not rotate the key: it is not the problem.
- `404`: Unknown method or unknown tool (JSON-RPC error `-32601`).
- `429`: Rate limited.

---

[API](https://skmtc.dev/fidren/apis/fidren-decision-api.md) · [All operations](https://skmtc.dev/fidren/apis/fidren-decision-api/llms.txt) · [OpenAPI document](https://skmtc.dev/fidren/apis/fidren-decision-api/revisions/d4b4dafcb345?raw)