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call_tool

Call any tool on a mounted MCP server by providing its qualified ID and arguments, enabling direct use of server-specific functions.

Instructions

Call a qualified tool (server.tool) on a mounted MCP server with arguments.

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": {
      "id": "<id>"
    },
    "name": "call_tool"
  }
}

Input Schema

Name	Required	Description	Default
`id`	Yes	qualified id, e.g. github.create_pull_request
`args`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.0Aug 8, 2026

TDQS

C2.9/5.0

Behavior2/5

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

With no annotations, the description must disclose behavioral traits but only states the basic operation. It does not mention potential side effects of executing a tool, error handling, server requirements, or whether the call is read-only or mutating. The phrase 'Call' implies execution, but no safety or failure details are given.

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 sentence that conveys the essential action without any fluff. It is front-loaded and every word contributes to understanding the tool's purpose. This is an example of efficient, concise writing.

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

Completeness2/5

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

For a generic tool with no output schema, the description is too minimal. It does not explain the return value, how the target tool's response is packaged, or what 'qualified' means. Given the tool's complexity as a dynamic invoker, more context is needed to fully understand its behavior.

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 coverage is 50%, with 'id' described but 'args' undocumented. The description adds the 'server.tool' format for the id, which helps, but does not explain the structure or purpose of 'args'. It partially compensates for the coverage gap but leaves significant ambiguity for a key parameter.

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 clearly states the action ('Call') and resource ('a qualified tool (server.tool) on a mounted MCP server'), which gives a precise idea of the tool's function. However, it does not explicitly distinguish this from sibling tools like load_tool or list_providers, though the name and mention of 'server.tool' imply it is for invocation.

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

Usage Guidelines2/5

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

The description provides no guidance on when to use this tool versus alternatives. It does not mention alternatives, exclusions, or prerequisites beyond the schema. The implied usage is to call any qualified tool, but the lack of any context for selection makes it weak.

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