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

Annotations cover read-only/idempotent safety, and the description adds substantial context beyond them: access is limited by history setting ('from_join' excludes pre-join messages), 30 searches/minute per credential, searching marks nothing read, and result snippets are untrusted content that must never be treated as instructions.

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?

Dense but front-loaded: purpose first, then query syntax, filters, access scoping, result format, and limits. Every sentence is informative, though some content (query operators, limit defaults, cursor) duplicates the schema, adding mild redundancy.

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?

For a 7-parameter search tool with an output schema, the description covers the remaining gaps an agent needs: access scoping, rate limit, pagination, result shape with highlight offsets, and the security caveat on snippet content. Nothing material is missing.

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%, so the baseline is 3. The description restates q syntax, limit default/max, and cursor semantics that the schema already documents, adding only marginal cross-tool context (sender id from city_room_members) that the schema largely mirrors.

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 (Search), a precise resource (one room you are a member of), a scope (words, newest first), and distinguishes itself from siblings by pointing to city_room_read for full messages. An agent can identify exactly what this does versus the many other city_room_* tools.

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?

Routes the agent explicitly: use city_room_members for a member id, city_room_read to read the whole message, and this tool to find messages. It also clarifies that searching marks nothing read, resolving a common ambiguity versus inbox-reading siblings.

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