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

Annotations already cover safety (readOnlyHint=true, openWorldHint=false), and the description adds real behavioral detail beyond them: excerpt-around-hit results, the id needed for the read_note follow-up, and the exact-phrase-to-individual-words fallback. It stops short of describing ranking order or how many results a broad query yields, so not a full 5.

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?

Purpose and scope are front-loaded in the first sentence, then return shape, then query-phrasing advice, then the sibling alternative. Four sentences with no filler and no repetition of schema constraints like the 1-20 limit.

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?

With no output schema, the description carries the burden and discharges it: it states what comes back (excerpt plus id), which tool consumes that id, and how matching degrades. An agent can call this correctly and chain to read_note without further inspection.

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 still earns a bump by adding usage semantics the schema lacks, namely that the query should be the user's own words and how a zero-hit exact phrase degrades to per-word matching.

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?

Specific verb ('Full-text search') plus an explicitly enumerated scope ('notes, todos, saved words and the items on their tag pages'), and it names list_notes as the browsing alternative so it is distinguishable from siblings without opening a 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?

Gives explicit when-to-use guidance including a worked example of query phrasing ('what did I decide about the billing migration' -> 'billing migration') and names the alternative (list_notes) for tag/folder/date browsing, spelling out the condition that selects it.

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