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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds the endpoint (GET /api/v2/chat/search) and the mixed query/filter requirement, but says nothing about pagination behavior, result caps, or rate limits despite the 'next' cursor in the schema.

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 compact sentences with the core scope stated first and the query/filter rule immediately after. The trailing API endpoint is minor but slightly non-essential padding for an agent that only needs invocation semantics.

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 6-parameter search tool with nested filter objects and no output schema, the description covers the required combination and the two key search modes. Pagination, sort, and limit are left entirely to the schema, which is acceptable but leaves a small gap.

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 baseline is 3. The description repeats the examples already present in the schema for 'filter' and 'message_filter' rather than adding new meaning, offering no added semantic value beyond the structured fields.

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+resource ('Search messages across channels'), which clearly separates it from read-oriented siblings like stream_get_message and stream_query_threads. It is clear but does not explicitly name an alternative tool, so it stops short of full sibling differentiation.

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 states the invocation constraint: scope with a channel 'filter' plus EITHER a full-text 'query' OR a 'message_filter' object. That EITHER/OR rule is genuinely actionable. It lacks when-not guidance and does not name alternative search paths, so it is not a 5.

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