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

The description repeats 'Read-only' which is already in the annotations, and adds a GraphQL implementation detail, but it does not disclose behavioral traits beyond that, such as permissions, pagination, or response format. The optional user filter is already captured by the schema, so no new behavioral information is added.

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 concise and front-loaded with the core purpose. The 'Read-only' phrase is redundant with the annotation, but the GraphQL note adds useful technical context without excessive length.

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 simple read-only, single-parameter tool, the description is adequate. It does not explain return values, but there is no output schema and the tool's purpose is straightforward. The sibling context and annotations fill most gaps.

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 description for user_id fully covers the parameter semantics ('Get conversations between the current user and this user id'), and the description adds no new meaning beyond that. With 100% schema coverage, a baseline of 3 is appropriate.

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 with a specific verb and resource: 'List messaging conversations.' It also mentions the optional user filter, distinguishing it from sibling list tools like appointments, documents, or forms.

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 provides clear context for when to use the tool (listing conversations, optionally filtered by user) but does not explicitly mention alternatives or exclusions. Sibling names make the distinction obvious, so this is sufficient.

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