What does 200 mean on GET /similar?

Semantic neighbours of the seed passage.

What does 400 mean on GET /similar?

This node has no embedder configured, so it cannot answer by meaning.

What does 401 mean on GET /similar?

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 /similar?

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.

More like this — GET /similar

get /similar

Request

curl \
  -H "x-api-key: $UNLOB_API_KEY" \
  "https://api.unlob.com/similar?id=<id>"

Behaviour

Use it when a result is nearly what you wanted — it searches by meaning from that passage rather than from words you have to guess.

Costs 1 credit.

Parameters

Name	Type	Description
`id`required	string	Seed passage id.
`limit`	integer	Maximum hits, default 10, maximum 100 (a larger value is clamped; `total` still reports the real match count).

Responses

Status	Meaning
`200`	Semantic neighbours of the seed passage.
`400`	This node has no embedder configured, so it cannot answer by meaning.
`401`	Missing, unknown or revoked key. A key minted moments ago can answer 401 until it propagates to the serving fleet.
`404`	No such passage id.
`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.

Response body

WebSearchResponse

Name	Type	Description
`facets`	object	Present only when facets=true
`mode`required	"keyword" \| "semantic" \| "hybrid"	The mode actually used
`partial`	boolean	true when at least one shard failed or timed out — the answer is short because a slice of the corpus was unreachable, NOT because that is all there is. Never treat a partial result as complete.
`results`required	object[]	—
`routed`required	boolean	true when the router chose the vertical, false when you named it
`total`required	integer	—
`vertical`	string \| null	The vertical actually queried

The same call over MCP

This capability is similar 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": "similar",
    "arguments": {
      "id": "<id>"
    }
  }
}

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 /similar?: Semantic neighbours of the seed passage.
What does 400 mean on GET /similar?: This node has no embedder configured, so it cannot answer by meaning.
What does 401 mean on GET /similar?: Missing, unknown or revoked key. A key minted moments ago can answer 401 until it propagates to the serving fleet.
What does 404 mean on GET /similar?: No such passage id.
What does 429 mean on GET /similar?: 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.