> ## Documentation Index
> Fetch the complete documentation index at: https://tyk.io/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# MCP Gateway Access Logs

> MCP-specific fields available in Tyk Gateway structured access logs, including JSON-RPC method, primitive type, primitive name, and error code.

When Tyk Gateway processes an MCP request, it adds four MCP-specific fields to the structured access log record for that request. These fields let you filter, aggregate, and analyze MCP traffic in your log management tooling using the same access log pipeline you use for REST APIs.

For an overview of all MCP observability signals, see [MCP observability](https://tyk.io/docs/ai-management/mcp-gateway/mcp-observability.md).

## Prerequisites

Access logging must be enabled in your Tyk Gateway configuration. Set `access_logs.enabled` to `true` in `tyk.conf`. See [Enabling Access Logs](https://tyk.io/docs/api-management/logs/access-logs.md#enabling-access-logs).

## MCP Fields

The following fields are added to access log records for MCP requests. Each field is only included when it has a non-empty value; fields are omitted from the record entirely when not applicable.

| Field | Type | Description |
| - | - | - |
| `api_type` | string | API protocol type. Always `mcp` for MCP requests. |
| `mcp_method` | string | JSON-RPC method invoked, for example `tools/call`, `resources/read` or `server/discover`. Present on all MCP requests. |
| `mcp_primitive_type` | string | MCP primitive category: `tool`, `resource`, or `prompt`. Present only when a primitive was matched. |
| `mcp_primitive_name` | string | Name of the specific tool, resource, or prompt invoked, for example `get_current_weather`. Present only when a primitive was matched. |
| `mcp_error_code` | integer | JSON-RPC error code of a failed request. Present only when the request failed. |

The `mcp_error_code` field holds the code of Tyk's own error, or, when the upstream MCP server returns a JSON-RPC error, the code from its response. Tyk's codes depend on the protocol version the request uses. See [MCP Error Codes](https://tyk.io/docs/ai-management/mcp-gateway/error-codes.md) for the full list.

## Access Logs When the Proxy Fronts a Tyk-Managed REST API

When an MCP proxy is [generated directly from a Tyk-managed REST API](https://tyk.io/docs/ai-management/mcps/api-to-mcp.md) rather than fronting a remote MCP server, a single `tools/call` request produces two separate access log entries when access logs are enabled on the Gateway.

The first entry is for the MCP proxy request itself, and carries the MCP fields described above. The second is for Tyk's internal call into the paired source REST API, dispatched through the gateway's standard request handling. That second entry has no MCP fields at all: its `api_type` reflects the source API's own type (`oas` for a Tyk OAS API), and it is otherwise indistinguishable from a request made directly against that API.

```json expandable theme={null}
{
  "api_id": "orders-mcp",
  "api_name": "Orders MCP Proxy",
  "api_type": "mcp",
  "client_ip": "10.0.0.42",
  "latency_total": 187,
  "method": "POST",
  "mcp_method": "tools/call",
  "mcp_primitive_name": "get_order_status",
  "mcp_primitive_type": "tool",
  "path": "/mcp",
  "prefix": "access-log",
  "status": 200,
  "trace_id": "4bf92f3577b34da6a3ce929d0e0e4736"
}
```

```json expandable theme={null}
{
  "api_id": "orders-rest",
  "api_name": "Orders REST API",
  "api_type": "oas",
  "client_ip": "10.0.0.42",
  "latency_total": 142,
  "method": "GET",
  "path": "/orders/{id}/status",
  "prefix": "access-log",
  "status": 200,
  "trace_id": "4bf92f3577b34da6a3ce929d0e0e4736"
}
```

If [OpenTelemetry tracing](https://tyk.io/docs/api-management/traces.md) is enabled alongside access logging, both entries carry the same `trace_id`: Tyk dispatches the internal call to the source API within the same trace as the originating MCP request, so the two entries are spans of one trace rather than unrelated hits. Without tracing enabled, there is no shared identifier between the two entries, so correlate them by timestamp. The proxy's own `latency_total` includes the time spent on the source API call, so it is always the larger of the two figures.

> [!NOTE]
>
> This dual-record pattern isn't unique to access logs. The Dashboard's [MCP analytics](https://tyk.io/docs/ai-management/mcp-gateway/mcp-analytics.md) charts, and the Tyk Pump analytics pipeline underneath them, follow the same rule: only the MCP proxy's own record is recorded as MCP traffic, so the source API's analytics include this internal traffic indistinguishably alongside any direct hits it receives. See [Tyk Pump](https://tyk.io/docs/api-management/tyk-pump.md) for how analytics records are processed and stored.

## Configuring Which Fields to Include

By default, each record includes all available fields. To log only some fields, use an access log template. See [Access Log Templates](https://tyk.io/docs/api-management/logs/access-logs.md#access-log-templates). Add `api_type` and the four `mcp_` fields to the template to keep the MCP detail.

## Example Log Records

A successful `tools/call` request produces a record similar to the following:

```json theme={null}
{
  "api_id": "my-weather-mcp",
  "api_name": "Weather MCP Proxy",
  "api_type": "mcp",
  "client_ip": "10.0.0.42",
  "latency_total": 312,
  "method": "POST",
  "mcp_method": "tools/call",
  "mcp_primitive_name": "get_current_weather",
  "mcp_primitive_type": "tool",
  "path": "/mcp",
  "prefix": "access-log",
  "status": 200
}
```

A request that fails at the gateway due to a missing or invalid key produces a record with `mcp_error_code` set. Tyk reads the JSON-RPC body before it checks the key, so the record also has the primitive fields:

```json theme={null}
{
  "api_id": "my-weather-mcp",
  "api_type": "mcp",
  "client_ip": "10.0.0.42",
  "latency_total": 4,
  "method": "POST",
  "mcp_error_code": -32001,
  "mcp_method": "tools/call",
  "mcp_primitive_name": "get_current_weather",
  "mcp_primitive_type": "tool",
  "path": "/mcp",
  "prefix": "access-log",
  "status": 401
}
```

For a request that uses `2026-07-28`, the same failure records `-33001`.

An `initialize` lifecycle call produces a record with no `mcp_primitive_type`. Its `mcp_primitive_name` is the method name:

```json theme={null}
{
  "api_id": "my-weather-mcp",
  "api_type": "mcp",
  "client_ip": "10.0.0.42",
  "latency_total": 18,
  "method": "POST",
  "mcp_method": "initialize",
  "mcp_primitive_name": "initialize",
  "path": "/mcp",
  "prefix": "access-log",
  "status": 200
}
```