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

Annotations declare readOnlyHint=true, and the description adds behavioral context by stating it returns 'in-process' metrics (snapshot at call time) and describes the series structure (counter with tool/status labels, histogram with sum/count). No contradictions.

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

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

The description is three well-structured sentences. The first sentence states the core purpose, the second lists the series (adding detail), and the third provides usage guidance. Every sentence is informative and no waste.

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

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

Given no parameters, annotations indicating read-only, and an output schema, the description is complete: it explains what the tool returns and when to use it, covering all needed information for an agent.

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

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

No parameters exist, and the description adds value by explaining the output structure, which is helpful since the input schema is empty and the output schema provides structure.

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

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

The description clearly states it returns Prometheus-format metrics for the MCPg server, listing specific series (counter and histogram) and their fields. It distinguishes itself from siblings by mentioning when it's useful (when HTTP /metrics endpoint is unreachable or via MCP protocol).

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

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

The description explicitly states when to use the tool: when the HTTP /metrics endpoint is unreachable (e.g., over stdio) or to fetch via MCP protocol. While it doesn't mention when not to use, it provides clear context that makes the usage scenario obvious.

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