What does 200 mean on GET /path?

The node chain, or found=false when none exists.

What does 401 mean on GET /path?

Missing, unknown or revoked key. A key minted moments ago can answer 401 until it propagates to the serving fleet.

What does 429 mean on GET /path?

Over the per-minute rate (spent in credits), or a hard-capped key without the credits this call costs. `retry-after` is present on the rate-limit case only.

Connect two passages — GET /path

get /path

Request

curl \
  -H "x-api-key: $UNLOB_API_KEY" \
  "https://api.unlob.com/path?a=<a>&b=<b>"

Behaviour

Returns the node chain between them: passages (p:), hosts (h:), stories (s:), topics (t:), entities (e:). `found: false` means no chain exists within the corpus, which is itself an answer — these two things are not connected in anything we hold.

Costs 2 credits; a call that runs and fails costs 1.

Parameters

Name	Type	Description
`a`required	string	Start passage id. `from` is accepted as an alias, because a spec published elsewhere named it that way.
`b`required	string	Goal passage id. `to` is accepted as an alias.

Responses

Status	Meaning
`200`	The node chain, or found=false when none exists.
`401`	Missing, unknown or revoked key. A key minted moments ago can answer 401 until it propagates to the serving fleet.
`429`	Over the per-minute rate (spent in credits), or a hard-capped key without the credits this call costs. `retry-after` is present on the rate-limit case only.

The same call over MCP

This capability is path on the MCP server, taking the same parameters and returning the same body. A parity test in the API fails the build if the two ever diverge, so you can read either reference and use the other.

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "path",
    "arguments": {
      "a": "<a>",
      "b": "<b>"
    }
  }
}

Most clients build that frame for you — see Connect a client.

See Errors for what to do with each status, and Retries and backoff for which are worth repeating.

FAQ

What does 200 mean on GET /path?: The node chain, or found=false when none exists.
What does 401 mean on GET /path?: Missing, unknown or revoked key. A key minted moments ago can answer 401 until it propagates to the serving fleet.
What does 429 mean on GET /path?: Over the per-minute rate (spent in credits), or a hard-capped key without the credits this call costs. `retry-after` is present on the rate-limit case only.