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MikkoParkkola

MCP Gateway

by MikkoParkkola
OverviewSchemaRelated ServersScoreDiscussions
Rust
Hybrid

Invoke Tool

gateway_invoke

Invoke tools across backend servers through a unified gateway with authentication, rate limiting, caching, and failsafe middleware. Discover available tools first using gateway_search_tools.

Instructions

Invoke any tool on any backend server. Routes through the gateway's auth, rate-limit, caching, and failsafe middleware. Use gateway_search_tools first to discover the right tool and server.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
argumentsNoTool arguments
serverYesBackend server name
toolYesTool name to invoke

Implementation Reference

  • benchmarks/token_savings.py:120-144 (schema)
    The tool definition (schema) for "gateway_invoke". Note that the actual handler implementation logic resides in the binary `mcp-gateway` (as per the context in `npm/run.js`), while this file defines its expected schema for benchmarking purposes.
        "name": "gateway_invoke",
    "description": (
        "Invoke a specific tool on a specific backend server. "
        "Pass the server name, tool name, and arguments. "
        "The gateway routes the request and returns the result."
    ),
    "inputSchema": {
        "type": "object",
        "properties": {
            "server": {
                "type": "string",
                "description": "Name of the backend MCP server.",
            },
            "tool": {
                "type": "string",
                "description": "Name of the tool to invoke.",
            },
            "arguments": {
                "type": "object",
                "description": "Arguments to pass to the tool.",
            },
        },
        "required": ["server", "tool"],
    },
},

Tool Definition Quality

A4.4/5.0
Behavior4/5

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

The description adds valuable behavioral context beyond annotations by specifying that it 'Routes through the gateway's auth, rate-limit, caching, and failsafe middleware.' While annotations provide readOnlyHint=false and openWorldHint=true, the description elaborates on the gateway's processing pipeline, which helps the agent understand the execution environment and potential side effects.

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 perfectly concise with two sentences that each earn their place: the first states the core functionality and behavioral traits, the second provides crucial usage guidance. No wasted words, front-loaded with essential information.

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?

Given the tool's complexity (invoking arbitrary tools with middleware routing) and lack of output schema, the description does well by explaining the gateway middleware and discovery prerequisite. However, it doesn't detail response formats, error handling, or specific auth/rate-limit implications, leaving some gaps for a tool with openWorldHint=true and no 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?

With 100% schema description coverage, the schema already documents all three parameters (arguments, server, tool) adequately. The description doesn't add specific meaning about parameter usage beyond implying that 'server' and 'tool' should be discovered via gateway_search_tools, which is minimal additional value. Baseline 3 is appropriate when schema does the heavy lifting.

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 specific action ('Invoke any tool on any backend server') and distinguishes it from siblings by mentioning routing through gateway middleware and the need to use gateway_search_tools first. It explicitly names the resource (tools on backend servers) and the verb (invoke) with clear scope.

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

Usage Guidelines5/5

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

The description provides explicit guidance on when to use this tool ('Use gateway_search_tools first to discover the right tool and server') and implies when not to use it (when you already know the specific tool from other sibling tools). It names an alternative (gateway_search_tools) for discovery, making usage context very clear.

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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