OpenAPI $ref resolver

Inline every local `$ref` in an OpenAPI 3.x or Swagger 2.x document so downstream tools see a self-contained spec. Send POST /api/openapi-resolve-refs with the required field spec and pay $0.001 per call over x402 or MPP, or call it free by solving a proof-of-work challenge. It returns a JSON object with spec, resolved, circular, unresolved and external.

Resolves `#/components/...` (OpenAPI) and `#/definitions/...` (Swagger) JSON-pointer refs anywhere in the document, including inside components themselves. Per-branch cycle detection: if A→B→A, the second A is left as a `$ref` and recorded under `circular`. External refs (http://, file://, ./other.yaml) are never fetched - they're reported under `external` and left as-is. Sibling keys of `$ref` (e.g. a `description` next to a `$ref`) are dropped to match JSON Schema Draft 7 / OpenAPI 3.0 semantics. Returns the dereffed spec plus `resolved` (count inlined) and arrays of any refs that couldn't be inlined. Pure CPU - deterministic, no network.

Category: Data conversion · Tags: openapi swagger ref dereference resolve api

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Parameters

Example request

curl -i -X POST https://agent402.tools/api/openapi-resolve-refs \
  -H "Content-Type: application/json" \
  -d '{"spec":{"openapi":"3.0.0","info":{"title":"Demo","version":"1.0.0"},"paths":{"/users/{id}":{"get":{"parameters":[{"$ref":"#/components/parameters/UserId"}],"responses":{"200":{"description":"ok","content":{"application/json":{"schema":{"$ref":"#/components/schemas/User"}}}}}}}},"components":{"schemas":{"User":{"type":"object","properties":{"id":{"type":"string"},"name":{"type":"string"}}}},"parameters":{"UserId":{"name":"id","in":"path","required":true,"schema":{"type":"string"}}}}}}'

Without payment this returns HTTP 402 Payment Required with the exact price for openapi-resolve-refs; any x402 v2 or MPP client pays it and retries.

Example response

{
  "spec": {
    "openapi": "3.0.0",
    "info": {
      "title": "Demo",
      "version": "1.0.0"
    },
    "paths": {
      "/users/{id}": {
        "get": {
          "parameters": [
            {
              "name": "id",
              "in": "path",
              "required": true,
              "schema": {
                "type": "string"
              }
            }
          ],
          "responses": {
            "200": {
              "description": "ok",
              "content": {
                "application/json": {
                  "schema": {
                    "type": "object",
                    "properties": {
                      "id": {
                        "type": "string"
                      },
                      "name": {
                        "type": "string"
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    },
    "components": {
      "schemas": {
        "User": {
          "type": "object",
          "properties": {
            "id": {
              "type": "string"
            },
            "name": {
              "type": "string"
            }
          }
        }
      },
      "parameters": {
        "UserId": {
          "name": "id",
          "in": "path",
          "required": true,
          "schema": {
            "type": "string"
          }
        }
      }
    }
  },
  "resolved": 2,
  "circular": [],
  "unresolved": [],
  "external": []
}

From an MCP client

catalog.call {
  "slug": "openapi-resolve-refs",
  "params": {
    "spec": {
      "openapi": "3.0.0",
      "info": {
        "title": "Demo",
        "version": "1.0.0"
      },
      "paths": {
        "/users/{id}": {
          "get": {
            "parameters": [
              {
                "$ref": "#/components/parameters/UserId"
              }
            ],
            "responses": {
              "200": {
                "description": "ok",
                "content": {
                  "application/json": {
                    "schema": {
                      "$ref": "#/components/schemas/User"
                    }
                  }
                }
              }
            }
          }
        }
      },
      "components": {
        "schemas": {
          "User": {
            "type": "object",
            "properties": {
              "id": {
                "type": "string"
              },
              "name": {
                "type": "string"
              }
            }
          }
        },
        "parameters": {
          "UserId": {
            "name": "id",
            "in": "path",
            "required": true,
            "schema": {
              "type": "string"
            }
          }
        }
      }
    }
  }
}

On the hosted connector at https://agent402.tools/mcp, catalog.call runs openapi-resolve-refs free (rate-limited, no wallet). Local install: npx -y agent402-mcp.

Errors and behavior

• spec is required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Free tier: no outbound network call leaves the server for this tool, so proof-of-work (16 leading zero bits of sha256) pays for it.
• A GET or HEAD to /api/openapi-resolve-refs returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
client.setSpendControls?.(false); // keep your own spending ceiling in code
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/openapi-resolve-refs", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "spec": {
      "openapi": "3.0.0",
      "info": {
        "title": "Demo",
        "version": "1.0.0"
      },
      "paths": {
        "/users/{id}": {
          "get": {
            "parameters": [
              {
                "$ref": "#/components/parameters/UserId"
              }
            ],
            "responses": {
              "200": {
                "description": "ok",
                "content": {
                  "application/json": {
                    "schema": {
                      "$ref": "#/components/schemas/User"
                    }
                  }
                }
              }
            }
          }
        }
      },
      "components": {
        "schemas": {
          "User": {
            "type": "object",
            "properties": {
              "id": {
                "type": "string"
              },
              "name": {
                "type": "string"
              }
            }
          }
        },
        "parameters": {
          "UserId": {
            "name": "id",
            "in": "path",
            "required": true,
            "schema": {
              "type": "string"
            }
          }
        }
      }
    }
  }),
});

No wallet? Pay with compute

Fetch a challenge, solve the sha256 puzzle (16 leading zero bits, a fraction of a second of CPU), and resend with the X-Pow-Solution header:

import { createHash } from "node:crypto";
const lz = (b) => { let t = 0; for (const x of b) { if (!x) { t += 8; continue; } t += Math.clz32(x) - 24; break; } return t; };
const c = await (await fetch("https://agent402.tools/api/pow/challenge?slug=openapi-resolve-refs")).json();
let n = 0;
while (lz(createHash("sha256").update(c.challenge + ":" + n).digest()) < c.difficulty) n++;
await fetch("https://agent402.tools/api/openapi-resolve-refs", { method: "POST", headers: { "X-Pow-Solution": c.token + ":" + n, "Content-Type": "application/json" }, body: JSON.stringify({"spec":{"openapi":"3.0.0","info":{"title":"Demo","version":"1.0.0"},"paths":{"/users/{id}":{"get":{"parameters":[{"$ref":"#/components/parameters/UserId"}],"responses":{"200":{"description":"ok","content":{"application/json":{"schema":{"$ref":"#/components/schemas/User"}}}}}}}},"components":{"schemas":{"User":{"type":"object","properties":{"id":{"type":"string"},"name":{"type":"string"}}}},"parameters":{"UserId":{"name":"id","in":"path","required":true,"schema":{"type":"string"}}}}}}) });

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