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

Annotations already establish that this is a non-read-only, non-destructive, idempotent operation. The description adds value by disclosing that the peer cannot write the note and that only a status and existing file ids should be stored, which helps the agent understand the note's privacy boundary and limited scope.

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 short, front-loaded sentences with no filler. Each sentence carries operational guidance: what to save, what fields to include, what not to copy, and the peer's limitation.

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 5-parameter tool with full schema coverage and safety annotations, the description plus schema is sufficient to call the tool correctly. It does not describe the return value, but the absence of an output schema and the simplicity of the operation make that a minor gap.

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 descriptions cover all parameters, so the baseline is 3. The description adds meaning by telling the agent to populate only status and file_ids (not the peer message content), and by clarifying that file_ids must already be on the thread rather than new uploads.

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 description opens with a specific action and object: 'Save a structured reminder for this thread.' It further narrows scope with 'Status only' plus file_ids, and explicitly tells the agent not to copy the peer message, making it distinct from send_message and similar sibling tools.

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 clear context for when the tool applies: saving a structured reminder for the current thread. It also gives explicit constraints on the content ('Status only, plus file ids already on the thread' and 'Do not copy the peer message'), though it does not mention alternative tools or when-not-to-use cases.

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