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

Annotations already declare readOnlyHint=true, and the description reinforces this with the GET /messages/{id} endpoint mapping, which is useful REST context. It stops there, disclosing nothing about auth requirements, rate limits, message retention, or error behavior for unknown ids.

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?

One front-loaded sentence naming the resource and returned fields, followed by a compact endpoint reference. No wasted words.

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?

With no output schema, the description usefully enumerates the returned fields (body, recipient, delivery status, parts, credit cost), which is exactly what compensates for the missing return definition. Only auth/error behavior is unaddressed.

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 description coverage is 100%, so the single message_id parameter is fully documented in the schema, including where ids originate. The description's 'by its id' adds no format or constraint detail beyond that baseline.

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 (get) and resource (one sent/received message) plus the fields returned, which clearly separates it from the singular-by-id case. It never names list_messages as the plural alternative, so the sibling contrast is only implicit rather than explicit.

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?

Usage is implied: fetch one message when you already have its id. There is no statement of when-not to use it or why an agent would pick this over bulksms_list_messages, leaving the selection logic to inference from the schema note that the id comes from list_messages or send_message.

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