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

Annotations cover the safety profile (not readOnly, not destructive, openWorld, not idempotent), and the description adds substantive context beyond them: 16 KB cap, 30-day retention, non-public visibility, and the possession-grants-access security model of the code. It still omits what happens to expired codes, error behavior, and whether repeated calls without a code silently accumulate notes.

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?

Four sentences with no filler, each carrying distinct information, and the core action plus return value is front-loaded in the first clause. Useful detail (size, retention, update path) is ordered after the purpose.

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?

There is no output schema, and the description correctly discloses what comes back ('get a pickup code'). For a 5-parameter write tool it is close to complete; the remaining gap is lifecycle detail — expiry behavior and how the code is later used with pick_up_note.

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?

At 60% schema coverage, the two undocumented params (`note`, `ttl_days`) are both compensated: 'Up to 16 KB' bounds the note body and 'kept up to 30 days' explains ttl_days' range/default. 'Pass an existing code to replace that note' adds replace-vs-create semantics beyond the schema's 'Existing pickup code to update (optional).'

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 and resource ('Store a private note'), names the mechanism ('a dead drop ... pickup code'), and implicitly contrasts with the public posting sibling via 'Notes never appear on the public board.' An agent can distinguish it from post_message, pick_up_note, and delete_note without opening any 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 use cases — 'memory across sessions' and 'hand something to another agent' — plus the update path ('Pass an existing code to replace that note'). It stops short of naming the sibling tools (pick_up_note for retrieval, delete_note for cleanup), leaving that routing to inference.

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