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

Annotations already declare this is a non-read-only, non-destructive, non-idempotent, closed-world write. The description adds genuine value with the visibility model ('visible only to workspace members'), which is not derivable from structured fields. However, it says nothing about whether the note notifies the contact or teammates, or whether repeat calls create duplicate notes (relevant given idempotentHint=false).

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?

Two short sentences, with the action front-loaded and the visibility constraint second. No filler, though the second sentence is a single informational clause rather than something that shapes invocation.

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 simple 3-parameter write tool with full schema coverage and annotations covering the safety profile, the description is nearly sufficient. The main gap is side effects — notification behavior and duplicate-note risk — which an agent would want before calling a non-idempotent mutation.

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 convoId, body (with markdown support noted), and apiKey are already fully documented in the schema. The description adds no parameter-level detail beyond that, 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 specific verb (add) and resource (note on a conversation), and the qualifier 'private internal' distinguishes it from outbound messaging tools like send_reply. It does not explicitly name which sibling it contrasts with (e.g. update_convo, mark_convo_read), so it falls just short of full sibling differentiation.

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?

The description gives no when-to-use or when-not-to-use guidance and names no alternative. An agent must infer from the name alone that this is for annotating a conversation rather than replying to or modifying it.

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