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cmcp

cmcp

by DeveshB-1
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
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Headers/Response Headers

headers_response_headers
Read-only

Echoes URL query parameters as custom response headers, enabling agents to test and inspect HTTP header behavior.

Instructions

This endpoint causes the server to send custom set of response headers. Providing header values as part of the URL parameters of a GET request to this endpoint returns the same as part of response header.

To send your own set of headers, simply add or replace the the URL parameters with your own set.

(Postman request: Headers/Response Headers | GET https://postman-echo.com/response-headers)

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "headers_response_headers"
  }
}

Input Schema

NameRequiredDescriptionDefault
ServerNoQuery parameter 'Server'apibin
Content-TypeNoQuery parameter 'Content-Type'text/html

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A3.7/5.0
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, openWorldHint and destructiveHint, so safety is covered; the description adds the important behavioral detail that inputs are echoed back verbatim as response headers, which is exactly the trait an agent needs to predict the result. It also nods at the external echo service by linking the concrete URL, though it doesn't discuss rate limits or failure cases.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The core behavior is front-loaded, but the two sentences restate each other ('returns the same as part of response header' vs 'add or replace the URL parameters') and there is a duplicated article ('the the'). It reads as filler rather than tight specification.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple, read-only echo endpoint with no output schema and full schema coverage, the description covers what the tool does, how to drive it, and the target URL. Only the absence of guidance about arbitrary versus fixed header keys and any sibling relationship keeps it from being complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so a baseline of 3 applies, but the description goes beyond it by explaining the semantics of arbitrary parameters — any key/value supplied becomes a response header, not just the two named schema properties. That is meaningful extra context about how parameters are interpreted.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a concrete action and resource: the endpoint returns the supplied URL parameters as response headers, and it includes the actual GET URL, which makes the behavior unambiguous. It does not explicitly differentiate itself from the sibling headers_request_headers, leaving the agent to infer the distinction between inspecting request headers and emitting response headers.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

'To send your own set of headers, simply add or replace the URL parameters with your own set' gives HOW to use the tool but no WHEN/WHEN-NOT guidance. There is no mention of the alternative headers_request_headers or of any prerequisites, so usage is only implied.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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