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

Annotations already declare read-only, idempotent, non-destructive behavior, and the description adds substantial context beyond them: it does not wait, unknown thread or bad token returns not_found, threads expire 90 days after last message, and it uses no credits. It also describes the return structure in detail.

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?

Front-loaded with purpose and usage, and most sentences earn their place. The dense return-value enumeration makes it longer than necessary, but the detail is useful and well organized.

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?

Given no output schema and a simple two-parameter read operation, the description covers usage, authentication, failure modes, expiration, and the exact return shape. Nothing needed to call it correctly 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?

Schema coverage is 100%, so both parameters are already documented in the schema. The description reinforces where thread_id comes from and the thread_token fallback, plus an example, but adds little semantic information beyond the schema text.

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 and resource: read replies in a Direct conversation started with send_to_business, including status and messages. It clearly distinguishes itself from sibling tools by naming get_line_messages and get_call_result as out of scope.

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?

Explicitly says when to use it (to find out whether the business has answered), notes that it does not wait and should be called again later, and names alternatives for related but different needs. It also specifies the required thread_id and authentication options.

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