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

Annotations already declare this as a safe, idempotent read-only operation with no external side effects. The description adds that the directory is static, contains no observations, and does not check live availability, which is useful context beyond the structured fields. It also includes a caveat about no independent factual verification, which is slightly misleading for a directory but not contradictory.

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 fairly long and mixes routing advice with directory contents and caveats. While every sentence has some purpose, the structure could be more front-loaded and concise. The example is helpful but adds length that may not earn its place for all agents.

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 the tool has no parameters, rich annotations, and an output schema, the description provides sufficient context. It explains what the directory contains and how it relates to other tools, though it could better clarify when the output schema should be consulted versus when to use the directory for routing.

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?

The tool takes no parameters, so baseline is 4. The description explicitly states 'Call with no arguments', reinforcing the schema's empty object. No additional semantic detail is needed.

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 the tool returns a static theme directory with English/French labels, geographic/time coverage, HTTP paths, and MCP tool names. This is a specific verb+resource that differentiates it from siblings like list_sources and catalog, though the routing guidance is somewhat verbose and could obscure the core purpose.

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?

Explicit when-to-use ('when the subject or supported scope is unknown') and when-not ('If the tool and inputs are known, call it directly'). It names alternatives (catalog, list_sources, domain-specific list_* tools) and their specific roles, leaving no ambiguity.

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