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

With no annotations provided, the description carries the full behavioral burden. It discloses the return fields (id, reason, sender, subject, file names), the access restriction (full member of the support project), and the meaning of each state. It does not cover pagination or sorting, but for a list tool this is adequate.

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?

The description is dense but well-structured: it front-loads the purpose, then explains states, then lists return fields, and ends with access control. Every sentence contributes meaning; no redundancy or fluff, though it is longer than strictly necessary.

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 list operation with one optional parameter and no output schema, the description covers the essential aspects: states, default, return fields, and access. It omits minor details like sorting or pagination, but these are not critical for an agent to call the tool correctly.

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 coverage is 100% for the 'state' parameter, so the baseline is 3. The description adds substantial value by explaining each state's meaning and the default behavior (held and failed), which goes beyond the schema's brief one-line description and helps the agent use the parameter correctly.

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 uses the specific verb 'List' and identifies the resource as 'letters to the support address' with a clear scope: letters that 'did not become part of a request.' It enumerates four states and clarifies the default behavior, distinguishing it from siblings like get_support_letter (singular) and list_support_queue (likely requests).

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 explains when to omit 'state' (to get held and failed) and defines each state, giving the agent context to decide if this tool fits. However, it does not explicitly name alternative tools or state when NOT to use it, relying on purpose clarity rather than explicit routing.

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