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

Annotations only declare readOnlyHint=true; the description adds non-obvious behavior: newest-first ordering, the default exclusion of activities, and the constraint that before_id/after_id can be used only one at a time. It also names the underlying endpoint.

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?

Front-loaded with the resource and return contents, then filters and pagination, ending with the endpoint. Dense and efficient, with almost 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?

For a read-only list tool with no output schema, it covers ordering, filtering behavior, and pagination semantics. The include expansion parameter is left to the schema, but nothing essential for correct invocation is 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?

Schema coverage is 100%, so the baseline is 3, but the description adds meaning beyond the schema: it explains what the key filters enum values (NOTES, MESSAGES, ALL) actually return and clarifies the mutual-exclusion rule for the pagination cursors that the schema does not state.

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 clear verb (read/list) and resource (a case's posts/timeline) and enumerates what it returns: customer messages, agent replies, internal notes. It is distinguishable from get_case and reply_to_case, though it never names a sibling explicitly.

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?

Provides useful in-tool routing via the default exclusion of activities and the filters='NOTES'/'MESSAGES'/'ALL' guidance, but gives no explicit when-to-use-this-vs-alternatives direction relative to sibling list/get/search tools.

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