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

Annotations already declare readOnlyHint/destructiveHint/openWorldHint, so 'Read-only' is largely redundant. The description does add genuinely new behavior: the result cap of 25 notes and the fact that matching lines are returned, which the schema does not expose. It omits pagination/truncation behavior if more than 25 notes match.

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?

A single dense sentence plus a short routing clause; the audience constraint and result bound are front-loaded, and every clause carries distinct 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?

For a one-parameter read tool with no output schema, the description covers audience, semantics, result shape (25 notes with matching lines), safety signal, and the alternative tool. Nothing needed to invoke it correctly 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 coverage is 100% and the single 'query' parameter is already documented as 'Words to look for; empty returns no results'. The description's 'full-text search' framing adds mild context but no syntax or matching-mode detail beyond the schema, so the 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?

Names a specific verb and resource ('full-text search across the brains you can read') and pins down scope with a concrete result bound ('up to 25 notes with their matching lines'). It also distinguishes itself from the sibling 'search' by audience (app window vs. model/chat), so an agent can tell the two apart without opening either 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?

Explicitly states the callers this tool is for ('Used only by the Cobrain app window (not by the model)') and names the alternative for the other case ('To search in the chat, use search'). Both a when-to-use and a when-not-to-use condition are present.

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