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

The annotations already declare readOnlyHint, idempotentHint, and non-destructive. The description adds minimal behavioral context beyond that, mentioning the inclusion of threadId but not expanding on side effects or edge cases. It does not contradict the annotations, so a neutral score is appropriate.

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 with no redundant words. It starts with the core purpose ('List SMS messages') and immediately provides the most important context, making it highly efficient.

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 list operation with a simple schema, the description covers all essential information: the action, the resource, the optional filters, the presence of threadId, and a pointer to the related sms_get tool. No critical details are 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?

The schema provides full descriptions for all parameters, so the baseline is 3. The description adds the phrase 'optional filters', which hints that the parameters are filter-like and optional, but does not provide additional detail beyond the schema. This is a slight enhancement but not significant.

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 lists SMS messages and includes the key attribute threadId. It also distinguishes itself from sms_get by mentioning that tool for full message detail, making its scope unambiguous.

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 explicitly says 'Use sms_get for full single-message detail', providing an alternative when needed. It implies when to use this tool for listing, though it does not detail specific use cases or prerequisites, but the list vs. get distinction is clear.

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