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

Annotations already carry readOnlyHint, destructiveHint=false, and openWorldHint=false, so 'Read-only' is restatement rather than added value. The genuine additions are the client-ownership constraint and the plan gating, which annotations cannot express. It does not describe what the returned notes look like, but the audience restriction largely makes that moot.

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 compact clauses with the highest-value constraint (not for the model) front-loaded, followed by the alternative. Slight terseness in 'on plans that include it' leaves the plan check implicit, but no sentence is wasted.

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-only, annotation-covered tool with no output schema, the description gives enough to decide correctly — and effectively routes the agent away from it toward `search`. The only real omission is what a returned 'similar note' contains, which matters little given the audience restriction.

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 parameter's unusual empty-string behavior ('empty only wakes the model up') is already documented in the schema. The description adds no further meaning about the query parameter, 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?

States a concrete resource and behavior: notes similar in meaning to the query. The parenthetical audience restriction ('only by the Cobrain app window, not by the model') sharpens the scope but also signals this is not a general-purpose search tool. A reader can tell it apart from `search` without opening the 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 says who should not call it (the model) and names the alternative for the normal case ('To search in the chat, use search'). It also flags an availability precondition ('on plans that include it'). Nothing about routing is left to inference.

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