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

Annotations already declare readOnlyHint=true, so the description need not restate safety. Beyond that, it adds no behavioral context — no pagination behavior, no statement about ordering (newest/oldest), and no note that the fixed max of 10 caps results despite the schema exposing limit and until cursors.

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 very short sentences with the purpose front-loaded and no padding. The trailing API-endpoint line adds little value but costs almost nothing in 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 list tool with full schema coverage, the description covers the core purpose adequately. However, with no output schema it says nothing about the shape or ordering of returned messages, and the notably low 'max 10' limit constraint is left entirely to the schema.

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 three parameters (id, limit, until) are already documented in-schema, establishing the baseline of 3. The description contributes no additional meaning about the id format, the until cursor semantics, or the limit cap.

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 specific verb and resource ('List the messages (emails) in a conversation') and the parenthetical '(emails)' implicitly separates it from sibling collection endpoints like list_conversation_comments, drafts, and posts. It never names a sibling explicitly, so differentiation relies on the agent inferring the distinction.

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 such as missive_get_message, missive_list_conversation_comments, or missive_list_conversations. The only additional line is an API endpoint mapping ('Missive: GET /conversations/{id}/messages'), which restates the operation rather than advising usage.

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