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

readOnlyHint=true already establishes the safe-read profile, so the bar is lower. The description adds real behavioral value beyond annotations by warning that message bodies may be redacted by FUB for privacy, which directly affects how an agent should interpret results.

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?

Two short sentences with no filler, and the resource plus filter scope is front-loaded before the endpoint reference. Size is well matched to a simple list tool.

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 read-only list tool with no output schema, annotations that cover safety, and fully documented params, the description supplies the one thing structured fields cannot: the privacy redaction caveat. Only the paging behavior is left implicit, and the schema's 'prefer next' note partially covers that.

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 all five parameters (limit, offset, personId, toNumber, fromNumber) are already documented in the schema. The description only restates the two filter axes at a high level, adding no syntax, default, or paging guidance beyond the schema.

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 the resource (text messages) and the two scoping keys (person or phone number), and names the underlying endpoint. It is clearly distinguishable from sibling read tools like fub_list_calls, though the 'list' verb itself is only carried by the name rather than the description.

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 says what can be filtered but never states when to reach for this tool versus alternatives (e.g., fub_list_calls for call history, or a search tool). No prerequisites, no note about combining or omitting filters to browse all messages.

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