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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), yet the description still adds a real operational prerequisite: 'Requires recordings:read scope.' That auth requirement is exactly the kind of context annotations don't carry. It omits whether the count is exact vs. capped for very large result sets.

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?

Three short sentences with no filler; the core purpose leads, the sibling pairing follows, and the auth prerequisite closes. Nothing could be removed without losing information.

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?

No output schema exists, yet the description says nothing about the shape of the result (raw integer? object with a count field?) or whether the count is bounded for large result sets. For a minimal tool with rich schema coverage this is adequate, but the return-value gap is real when there is no output schema to fall back on.

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?

Schema description coverage is 100%, including detailed account and workspace semantics, so parameter meaning is fully handled by the schema. The description only echoes 'search query' without adding format or matching-behavior detail, so baseline 3 applies.

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?

States a specific verb ('Count') and resource ('calls matching a search query'), so the agent knows exactly what it returns. It implicitly separates itself from hub_search_calls by pointing at it as the paginated companion, but never explicitly contrasts with the sibling hub_count_calls (count of all calls), which an agent could easily confuse with this tool.

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?

'Pair with `hub_search_calls` for paginated UIs' gives a concrete usage pattern and names the alternative tool to combine with. It stops short of when-not-to-use guidance (e.g., use hub_count_calls when you have no query filter), so the routing signal is clear but incomplete.

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