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

Annotations already cover readOnly/idempotent/non-destructive/closed-world, so the description goes beyond by disclosing that this is static directory content, contains no observations and no live availability check, requires inspecting data-response freshness, and makes no independent factual verification claim. These caveats add real behavioral value that annotations do not supply.

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?

Reasonably tight for the amount of routing information it must convey: purpose/contents sentence, a call-with-no-args instruction and example, a when-not clause, and a scope caveat. The caveat sentences ('no observations or live availability check', 'no independent factual verification claimed') are somewhat boilerplate-heavy, but each sentence still earns its place.

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?

An output schema exists, so return values needn't be restated; annotations already cover safety. Given that, the description is complete for a no-arg discovery tool — content, usage conditions, alternatives, and static-data caveats are all present, with only minor redundancy.

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 zero parameters, so there is nothing for the description to document; baseline for a parameterless tool is 4. The description correctly reinforces 'Call with no arguments', which aligns with the empty schema.

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 states a specific resource and its contents: a 'static theme directory with English/French labels, geographic and time coverage, HTTP directory paths and MCP data-tool names.' That is concrete enough to distinguish it from most siblings, though the opening clause frames it as usage advice rather than a crisp purpose statement, and the name ('list_topics') vs 'theme directory' wording is a slight mismatch.

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'), when-not ('If the tool and inputs are known, call it directly'), and named alternatives ('use domain-specific list_* tools only for missing identifiers or available periods', 'Use catalog for service policies/counts and list_sources for publishers/licenses'). Routing is unambiguous.

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