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WP EngineDocumentation

Count message tokens (Anthropic Messages API)

POST
/v1/messages/count_tokens
<?php


$client = new \GuzzleHttp\Client();


$response = $client->request('POST', 'https://api.ai.wpengine.com/v1/messages/count_tokens', [
  'body' => '{ "model": "anthropic/claude-sonnet-4-6", "messages": [ { "role": "user", "content": "example" } ], "system": "example" }',
  'headers' => [
    'Authorization' => 'Bearer <token>',
    'Content-Type' => 'application/json',
  ],
]);


echo $response->getBody();

Counts the input tokens a Messages request would consume, without creating a message or incurring model usage. Accepts the same request shape as /v1/messages minus max_tokens. Authentication matches /v1/messages: a WP Engine bearer token or an “x-api-key” header; API keys must carry the “chat:write” permission. Some models do not support token counting and return a 400 error.

Authorizations

Section titled “Authorizations”

Request Bodyrequired

Section titled “Request Bodyrequired”
Media typeapplication/json

Same shape as an Anthropic Messages request without max_tokens; system and tools are included in the count when supplied.

object
model
required
string
Example
anthropic/claude-sonnet-4-6
messages
required
Array<object>
object
role
required
string
Allowed values: user assistant
content
required

Message content: a plain string, or an array of content blocks (text, image, tool_use, tool_result, thinking, …).

system

System prompt, as a string or array of content blocks.

Responses

Section titled “Responses”

200

Section titled “200”

Token count for the supplied request

Media typeapplication/json
object
input_tokens
required

Tokens the supplied request would consume as input.

integer
Example
{
  "input_tokens": 14
}

400

Section titled “400”

Invalid request body or parameters, in Anthropic error envelope format (error type “invalid_request_error”).

Media typeapplication/json

Anthropic error envelope, as parsed by Anthropic SDKs.

object
type
required
string
Allowed values: error
error
required
object
type
required

Anthropic error type, e.g. “invalid_request_error”, “authentication_error”, “permission_error”, “not_found_error”, “request_too_large”, “rate_limit_error”, “overloaded_error”, “api_error”, or “content_policy_violation” (request content blocked by moderation policy when content moderation is enabled — never identifies which filter or category matched).

string
message
required
string
request_id

Correlation ID for this request, matching the X-Request-ID response header. Quote it in support reports.

string
Example
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "max_tokens is required and must be greater than zero",
    "request_id": "80f1e2c3a4b5c6d7e8f9a0b1c2d3e4f5"
  }
}

401

Section titled “401”

Missing or invalid credentials, in Anthropic error envelope format (error type “authentication_error”).

Media typeapplication/json

Anthropic error envelope, as parsed by Anthropic SDKs.

object
type
required
string
Allowed values: error
error
required
object
type
required

Anthropic error type, e.g. “invalid_request_error”, “authentication_error”, “permission_error”, “not_found_error”, “request_too_large”, “rate_limit_error”, “overloaded_error”, “api_error”, or “content_policy_violation” (request content blocked by moderation policy when content moderation is enabled — never identifies which filter or category matched).

string
message
required
string
request_id

Correlation ID for this request, matching the X-Request-ID response header. Quote it in support reports.

string
Example
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "max_tokens is required and must be greater than zero",
    "request_id": "80f1e2c3a4b5c6d7e8f9a0b1c2d3e4f5"
  }
}

Headers

Section titled “Headers”
WWW-Authenticate
string
Example
Bearer realm="ai-services"

403

Section titled “403”

Valid credentials but insufficient permission, in Anthropic error envelope format (error type “permission_error”). The same type is returned when billing isn’t set up for the account yet, because AI hasn’t been turned on for it in the User Portal or its setup hasn’t finished; the message says so. On /v1/messages, when content moderation is enabled, a 403 with error type “content_policy_violation” instead means the request content was blocked by content moderation policy; that response never identifies which filter or category matched.

Media typeapplication/json

Anthropic error envelope, as parsed by Anthropic SDKs.

object
type
required
string
Allowed values: error
error
required
object
type
required

Anthropic error type, e.g. “invalid_request_error”, “authentication_error”, “permission_error”, “not_found_error”, “request_too_large”, “rate_limit_error”, “overloaded_error”, “api_error”, or “content_policy_violation” (request content blocked by moderation policy when content moderation is enabled — never identifies which filter or category matched).

string
message
required
string
request_id

Correlation ID for this request, matching the X-Request-ID response header. Quote it in support reports.

string
Example
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "max_tokens is required and must be greater than zero",
    "request_id": "80f1e2c3a4b5c6d7e8f9a0b1c2d3e4f5"
  }
}

404

Section titled “404”

The requested model was not found or does not support this endpoint, in Anthropic error envelope format (error type “not_found_error”).

Media typeapplication/json

Anthropic error envelope, as parsed by Anthropic SDKs.

object
type
required
string
Allowed values: error
error
required
object
type
required

Anthropic error type, e.g. “invalid_request_error”, “authentication_error”, “permission_error”, “not_found_error”, “request_too_large”, “rate_limit_error”, “overloaded_error”, “api_error”, or “content_policy_violation” (request content blocked by moderation policy when content moderation is enabled — never identifies which filter or category matched).

string
message
required
string
request_id

Correlation ID for this request, matching the X-Request-ID response header. Quote it in support reports.

string
Example
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "max_tokens is required and must be greater than zero",
    "request_id": "80f1e2c3a4b5c6d7e8f9a0b1c2d3e4f5"
  }
}

413

Section titled “413”

Request body exceeds the size limit, in Anthropic error envelope format (error type “request_too_large”).

Media typeapplication/json

Anthropic error envelope, as parsed by Anthropic SDKs.

object
type
required
string
Allowed values: error
error
required
object
type
required

Anthropic error type, e.g. “invalid_request_error”, “authentication_error”, “permission_error”, “not_found_error”, “request_too_large”, “rate_limit_error”, “overloaded_error”, “api_error”, or “content_policy_violation” (request content blocked by moderation policy when content moderation is enabled — never identifies which filter or category matched).

string
message
required
string
request_id

Correlation ID for this request, matching the X-Request-ID response header. Quote it in support reports.

string
Example
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "max_tokens is required and must be greater than zero",
    "request_id": "80f1e2c3a4b5c6d7e8f9a0b1c2d3e4f5"
  }
}

429

Section titled “429”

Rate limit exceeded. The request was throttled at the edge; wait and retry later. The response body is a short HTML page generated by the load balancer, not a structured JSON error — clients should rely on the 429 status code rather than parsing the body.

Media typetext/html
string

502

Section titled “502”

Upstream provider returned an error, in Anthropic error envelope format (error type “api_error”).

Media typeapplication/json

Anthropic error envelope, as parsed by Anthropic SDKs.

object
type
required
string
Allowed values: error
error
required
object
type
required

Anthropic error type, e.g. “invalid_request_error”, “authentication_error”, “permission_error”, “not_found_error”, “request_too_large”, “rate_limit_error”, “overloaded_error”, “api_error”, or “content_policy_violation” (request content blocked by moderation policy when content moderation is enabled — never identifies which filter or category matched).

string
message
required
string
request_id

Correlation ID for this request, matching the X-Request-ID response header. Quote it in support reports.

string
Example
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "max_tokens is required and must be greater than zero",
    "request_id": "80f1e2c3a4b5c6d7e8f9a0b1c2d3e4f5"
  }
}

503

Section titled “503”

A required dependency (such as the authorization service) is temporarily unavailable, in Anthropic error envelope format (error type “overloaded_error”). Retry after a short delay with exponential back-off.

Media typeapplication/json

Anthropic error envelope, as parsed by Anthropic SDKs.

object
type
required
string
Allowed values: error
error
required
object
type
required

Anthropic error type, e.g. “invalid_request_error”, “authentication_error”, “permission_error”, “not_found_error”, “request_too_large”, “rate_limit_error”, “overloaded_error”, “api_error”, or “content_policy_violation” (request content blocked by moderation policy when content moderation is enabled — never identifies which filter or category matched).

string
message
required
string
request_id

Correlation ID for this request, matching the X-Request-ID response header. Quote it in support reports.

string
Example
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "max_tokens is required and must be greater than zero",
    "request_id": "80f1e2c3a4b5c6d7e8f9a0b1c2d3e4f5"
  }
}

default

Section titled “default”

Upstream provider error relayed with its original status code and translated into Anthropic error envelope format. The error type reflects the status code (e.g. “rate_limit_error” for 429, “overloaded_error” for 529).

Media typeapplication/json

Anthropic error envelope, as parsed by Anthropic SDKs.

object
type
required
string
Allowed values: error
error
required
object
type
required

Anthropic error type, e.g. “invalid_request_error”, “authentication_error”, “permission_error”, “not_found_error”, “request_too_large”, “rate_limit_error”, “overloaded_error”, “api_error”, or “content_policy_violation” (request content blocked by moderation policy when content moderation is enabled — never identifies which filter or category matched).

string
message
required
string
request_id

Correlation ID for this request, matching the X-Request-ID response header. Quote it in support reports.

string
Example
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "max_tokens is required and must be greater than zero",
    "request_id": "80f1e2c3a4b5c6d7e8f9a0b1c2d3e4f5"
  }
}