MCP Tool-Retrieval Gateway

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call_tool

Call a specific tool by name on its upstream server, forwarding arguments and returning the result. Enables direct invocation of tools discovered via semantic retrieval.

Instructions

Invoke a tool by name (as returned by find_tools) on whichever upstream server owns it, forwarding the given arguments, and return that server's result.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

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

Input Schema

Name	Required	Description	Default
`name`	Yes
`arguments`	No

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.2.0Aug 7, 2026

TDQS

A4/5.0

Behavior3/5

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

No annotations are provided, so the description carries the full burden. It discloses the core behavior of forwarding arguments and returning the server's result, but does not mention potential side effects (since invoking arbitrary tools may cause mutations), error handling, or permissions. The generic nature limits deeper transparency, but the forwarding and return behavior is clearly stated.

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

Conciseness5/5

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

The description is a single, front-loaded sentence with no fluff. Every part adds value: invocation, name source, routing, argument forwarding, and return behavior.

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 two-parameter proxy with an output schema, the description covers the key aspects: what it invokes, how to get the name, where it routes, and what it returns. It omits edge-case details like errors or timeouts, which is acceptable given the tool's simplicity and the presence of an output schema.

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

Parameters3/5

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

Schema description coverage is 0%, so the description must compensate. It does specify that the 'name' parameter comes from find_tools and that 'arguments' are forwarded, adding some meaning beyond the schema. However, it does not elaborate on argument structure or provide examples, leaving partial compensation.

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

Purpose5/5

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

The description clearly states the tool invokes a named tool, explicitly references find_tools for name discovery, and distinguishes itself from the sibling by focusing on invocation rather than discovery. The verb 'Invoke' and resource 'tool by name' make the purpose unambiguous.

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

Usage Guidelines4/5

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

The description ties usage to find_tools output ('as returned by find_tools'), providing clear context on when to use this tool. It lacks explicit exclusions or 'when not to use' guidance, but the reference to the sibling is strong contextual guidance.

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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