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

Annotations already mark it read-only, and the description adds useful behavioral context beyond that: 'full-window stored' clarifies the read scope, 'zero baseline is undefined' warns about division-by-zero cases, and 'Does not infer sentiment or equal collection coverage' sets expectations about limitations. No contradiction with annotations.

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?

Two sentences with no filler: the first states the function and scope, the second states the output and key caveats. Every clause adds information an agent needs.

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 complex nested schema and no output schema, the description covers the essential inputs and output semantics. Minor gaps remain around exact response shape and how limit/cursor relate to 'full-window' counts, but 'full-window' implies the counts are not paginated and the agent has enough to invoke the tool correctly.

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?

Top-level schema descriptions are absent, so the description must compensate; it does by explaining the core relationship between baseline and current ('two UTC periods with identical filters') and what is computed. The nested schema already documents individual filter fields, and the description adds the 'identical filters' constraint that is not otherwise explicit.

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 names a specific verb ('Compare'), a clear resource ('stored post and author counts'), and a distinctive scope ('across two UTC periods with identical filters'). This is enough for an agent to separate it from siblings like aggregate_posts or get_posts without needing to open the schema.

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 clearly establishes when to use it: period-over-period comparison of stored counts. It does not explicitly name alternative tools or state when not to use it, but the context is unambiguous and no misleading guidance is present.

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