search_threads

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

Beyond the readOnly/idempotent annotations, it discloses that spam is never returned, trash only with includeTrash, that each thread yields only a 5-message summary without bodies, that one page is returned per call, and that email content is untrusted and delimited by ⟦mail:ID⟧ fences with an explicit prompt-injection warning. That is substantive behavioral context annotations cannot carry.

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?

Front-loaded with purpose and scoping, then return shape, then pagination, then a security note, then a compact Args block. Dense but every sentence adds information an agent needs; nothing is redundant.

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?

Complete for a paginated search tool: scope, return shape, pagination mechanics, and injection-safety framing are all present, and an output schema exists to cover return structure precisely. An agent has everything needed to call this correctly on the first attempt.

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 0%, so the description must carry the load, and it does: query semantics with real Gmail syntax examples and the '' = all-threads rule, pageSize bounds (1 to 50, default 20), pageToken chaining from nextPageToken, and includeTrash default false. Every parameter gains meaning absent from the 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?

Opens with a specific verb+resource ('Search Gmail threads') and immediately scopes it with Gmail query syntax examples. It clearly distinguishes itself from get_thread and get_message by stating that bodies are excluded and pointing to those siblings for full reads.

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?

Explicitly routes deep reads to get_thread/get_message, explains pagination ('when nextPageToken is returned, pass it as pageToken'), and defines the empty-query default scope. It lacks an explicit 'use this instead of X when...' rule against other search-ish siblings, but no comparable sibling exists, so guidance is near-complete.

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