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

With only destructiveHint=true available, the description adds real behavioral context: the note is invisible to the customer, and the operation is non-idempotent (each call appends rather than upserts), which is exactly why a destructive/non-idempotent hint applies. It does not cover auth requirements, error modes, or what is returned.

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 short sentences, front-loaded with the operation type and scoping caveat; the endpoint is a bonus for traceability. Nothing is repeated from the name/title verbatim and no sentence is filler.

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 two-parameter write with no output schema and sparse annotations, the description covers what an agent needs: it's a write, it's non-idempotent, and the note is internal. Only missing piece is whether a note id or confirmation is returned, which matters slightly since no output schema exists.

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%, with both parameters documented in the schema, so the baseline is 3. The description adds nothing param-specific beyond the schema — it does not clarify body formatting (the schema already says 'Plain text') or what forms conversation_id can take.

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?

The opening token 'WRITE:' plus 'add an internal note to a conversation' gives a specific verb and resource, and the description immediately distinguishes visibility ('for agents only; the customer does not see it'). All siblings in the list are read tools, so the write nature is disambiguated up front.

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?

It states a clear conditional rule: 'Each call adds a NEW note, so do not repeat a call that succeeded,' which tells the agent when a retry is unsafe. It also implies the audience constraint that distinguishes this from a customer-facing reply, but it never names an explicit alternative tool or precondition (e.g., permissions).

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