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

Annotations already indicate readOnlyHint=false, and the description's mention of 'POST' reinforces the write nature without adding much new context. It references 'converse JSON format' without explanation, and does not disclose authentication requirements, rate limits, or failure behavior. The description adds minimal value beyond the annotations.

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 a single, efficient sentence that front-loads the core action and endpoint. However, its brevity leads to missing essential details, so it is concise but not optimally structured for completeness.

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 6 parameters and sibling tools that overlap in functionality, this description is too minimal. It does not explain when to choose this tool, what default channels are used, or how the 'converse JSON format' differs from alternatives. Although an output schema exists to cover return values, the lack of selection and operational context makes the description incomplete.

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 baseline is 3. The description's only parameter information ('Use to as fbId or phone') is redundant with the schema's existing property description for 'to'. No additional meaning is provided for other parameters like 'message', 'type', 'format', 'tag', or 'user_id'.

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 the tool's function: 'Send an outbound message to an end user' with a specific action verb and resource. It also mentions the endpoint and a key parameter nuance ('Use to as fbId or phone'). However, it does not distinguish this tool from sibling tools like send-converse-message or send-inbox-message, so it misses the highest score.

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?

There is no guidance on when to use this tool versus alternatives. The only usage hint ('Use to as fbId or phone') is a parameter detail, not a tool-selection guideline. No exclusions or alternative tools are mentioned, leaving the agent without contextual decision support.

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