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

Annotations (readOnlyHint, destructiveHint, idempotentHint) already indicate a safe, read-only operation. The description adds that it returns an array of specific fields (message_id, from, to, text, status, created_at, cost). It does not cover aspects like auth or rate limits, but given the annotations, this is sufficient.

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 two sentences: first covers purpose and filters, second states return structure. It is concise, front-loaded, and every sentence adds value.

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?

The description mentions return fields and optional filters. However, it does not explain pagination behavior beyond limit (e.g., how to get next page), sorting, or default ordering. Given the output schema exists (implied) and annotations cover safety, the description is slightly incomplete for a tool that may return partial results.

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?

The description adds meaning beyond the schema: it explains the direction enum values, specifies date_from format (ISO 8601), and notes the default limit (25) and maximum (100). Schema coverage is 100%, but the description enriches the details.

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 clearly states 'List recent Telnyx messages', specifies the resource (Telnyx messages), and mentions optional filters. The tool name and title are unambiguous. Among sibling Telnyx tools, this is the only one for listing messages, making its purpose distinct.

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 does not explicitly state when to use this tool versus alternatives like sending SMS or checking status. However, the sibling tools (e.g., sms_na, status) have clearly different purposes, so the usage context is implicitly clear but could be improved with explicit guidance.

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