Append session messages

Append one message or an ordered batch of up to 100 messages atomically.

POST/api/v2/sessions/{id}/messages

Authorization

AuthorizationBearer token (Anlyon API key) · headerrequired

Workspace API key sent as Authorization: Bearer <key>.

better-auth.session_tokenAPI key · cookierequired

Browser session used by dashboard-only operations.

Path parameters

idstringrequired

Public session identifier.

min length 1 · max length 100

Header parameters

X-Request-Idstring

Optional caller correlation ID. Unsafe or oversized values are replaced.

max length 128

Idempotency-Keystring

Stable retry key for a mutation. The key is claimed atomically before the handler runs, so concurrent retries execute the side effect at most once. Replaying the key for the same request (same method, path, workspace and JSON body) returns the original response with an X-Idempotent-Replay: true header. Reusing the key for a different request returns 409 with error code idempotency_key_reuse. A duplicate arriving while the first is still in flight waits and then replays; if the first does not finish in time the duplicate gets 409 idempotency_request_in_progress. Keys are retained for 24 hours. Only successful (2xx) responses are stored; a failed request frees the key so it can be retried.

min length 1 · max length 255

Request body

requiredapplication/json

One of:

object

rolestringrequired

Allowed:systemuserassistanttool

contentstringrequired

min length 1 · max length 1048576

toolCallIdstring

min length 1 · max length 200

metadataobject

runIdstring

Existing run in this API key environment for session-write spans.

max length 80

parentSpanIdstring

Optional parent span within runId.

max length 80

object

messagesSessionMessageInput[]required

min items 1 · max items 100

Show properties

Array of SessionMessageInput

rolestringrequired

Allowed:systemuserassistanttool

contentstringrequired

min length 1 · max length 1048576

toolCallIdstring

min length 1 · max length 200

metadataobject

runIdstring

Existing run in this API key environment for session-write spans.

max length 80

parentSpanIdstring

Optional parent span within runId.

max length 80

Responses

201

Messages appended.

successbooleanrequired

Allowed:true

dataobjectrequired

Show properties

sessionIdstringrequired

appendedintegerrequired

min 1 · max 100

messagesSessionMessage[]required

Show properties

Array of SessionMessage

indexintegerrequired

min 0

rolestringrequired

Allowed:systemuserassistanttool

contentstringrequired

toolCallIdstring | nullrequired

tokenCountintegerrequired

min 0

metadataobjectrequired

createdAtstring<date-time>required

400

Bad Request - Invalid input data

successbooleanrequired

requestIdstringrequired

Correlation ID matching the X-Request-Id response header.

errorobjectrequired

Show properties

codestring

messagestring

detailsobject

401

Unauthorized - Invalid or missing API key

successbooleanrequired

requestIdstringrequired

Correlation ID matching the X-Request-Id response header.

errorobjectrequired

Show properties

codestring

messagestring

detailsobject

402

Payment Required - Usage quota exceeded

successbooleanrequired

requestIdstringrequired

Correlation ID matching the X-Request-Id response header.

errorobjectrequired

Show properties

codestring

messagestring

detailsobject

403

Authenticated credential lacks the required scope or workspace access.

successbooleanrequired

requestIdstringrequired

Correlation ID matching the X-Request-Id response header.

errorobjectrequired

Show properties

codestring

messagestring

detailsobject

404

Not Found - Resource does not exist

successbooleanrequired

requestIdstringrequired

Correlation ID matching the X-Request-Id response header.

errorobjectrequired

Show properties

codestring

messagestring

detailsobject

429

Too Many Requests - Rate limit exceeded

successbooleanrequired

requestIdstringrequired

Correlation ID matching the X-Request-Id response header.

errorobjectrequired

Show properties

codestring

messagestring

detailsobject

Try it

Server

Base URLCustom base URLOverrides the selected server when set.

Authorization

Bearer token (Anlyon API key)Remember on this deviceInclude my values in samples

Parameters

X-Request-IdheaderOptional caller correlation ID. Unsafe or oversized values are replaced.idpath*Public session identifier.Idempotency-KeyheaderStable retry key for a mutation. The key is claimed atomically before the handler runs, so concurrent retries execute the side effect at most once. Replaying the key for the same request (same method, path, workspace and JSON body) returns the original response with an `X-Idempotent-Replay: true` header. Reusing the key for a different request returns `409` with error code `idempotency_key_reuse`. A duplicate arriving while the first is still in flight waits and then replays; if the first does not finish in time the duplicate gets `409 idempotency_request_in_progress`. Keys are retained for 24 hours. Only successful (2xx) responses are stored; a failed request frees the key so it can be retried.

Bodyapplication/json

Request body

Request

curl -X POST 'https://api.anlyon.com/api/v2/sessions/string/messages' \
  -H 'Authorization: Bearer YOUR_TOKEN' \
  -H 'Content-Type: application/json' \
  -d '{
  "role": "system",
  "content": "string",
  "toolCallId": "string",
  "metadata": {},
  "runId": "string",
  "parentSpanId": "string"
}'

const response = await fetch("https://api.anlyon.com/api/v2/sessions/string/messages", {
  method: "POST",
  headers: {
    "Authorization": "Bearer YOUR_TOKEN",
    "Content-Type": "application/json"
  },
  body: "{\n  \"role\": \"system\",\n  \"content\": \"string\",\n  \"toolCallId\": \"string\",\n  \"metadata\": {},\n  \"runId\": \"string\",\n  \"parentSpanId\": \"string\"\n}"
});

import requests

response = requests.post(
    "https://api.anlyon.com/api/v2/sessions/string/messages",
    headers={
        "Authorization": "Bearer YOUR_TOKEN",
        "Content-Type": "application/json"
    },
    data="{\n  \"role\": \"system\",\n  \"content\": \"string\",\n  \"toolCallId\": \"string\",\n  \"metadata\": {},\n  \"runId\": \"string\",\n  \"parentSpanId\": \"string\"\n}",
)

Response

{
  "success": true,
  "data": {
    "sessionId": "string",
    "appended": 1,
    "messages": [
      {
        "index": 0,
        "role": "system",
        "content": "string",
        "toolCallId": "string",
        "tokenCount": 0,
        "metadata": {},
        "createdAt": "2019-08-24T14:15:22Z"
      }
    ]
  }
}

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid request data",
    "details": {
      "url": "Invalid URL format"
    }
  }
}

{
  "success": false,
  "error": {
    "code": "AUTHENTICATION_ERROR",
    "message": "Invalid or missing API key"
  }
}

{
  "success": false,
  "error": {
    "code": "QUOTA_EXCEEDED",
    "message": "Daily message quota exceeded. Upgrade your plan to continue."
  }
}

{
  "success": false,
  "requestId": "req_0123456789abcdef0123456789abcdef",
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid request data",
    "details": {}
  }
}

{
  "success": false,
  "error": {
    "code": "NOT_FOUND",
    "message": "Resource not found"
  }
}

{
  "success": false,
  "error": {
    "code": "RATE_LIMIT_EXCEEDED",
    "message": "Rate limit exceeded. Please try again later."
  }
}