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

With no annotations, the description carries full behavioral burden and handles it well: it discloses what data is included, that HTML is converted to text, and the access-control rule distinguishing letters tied to issues from other letters. This is especially valuable for an operation that reveals potentially sensitive content.

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 compact sentences front-load the core behavior, then add only high-value context about ID sourcing and permissions. No filler or repetition of schema details.

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 single-parameter read operation with no output schema, the description covers return contents, how to get the ID, and who can read which letters. Nothing essential for correct invocation is missing.

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?

Although the schema already documents letterId as 'The letter's id,' the description adds meaning by explaining where to obtain the id—from list_support_letters or get_support_request's messages. This provenance is the key semantic gap and is filled beyond the schema's tautological description.

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?

Description uses a specific verb and resource: 'Read one letter to the support address whole.' It goes beyond a mere restatement by enumerating what the tool returns—quoted thread, signature, HTML part as text, and headers—and differentiates from get_support_request's comment content and list_support_letters.

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 gives clear context for use by stating that letterId comes from list_support_letters or from get_support_request's messages, and implies when the full letter is needed versus the abbreviated comment. It does not explicitly state when not to use this tool, but the context is sufficient for a read-only single-resource operation.

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