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

Annotations already declare destructive=true and idempotent=true, but the description adds substantial context beyond them: exactly what is destroyed (all messages, attachment bytes, search rows), what is preserved (owner tasks and updates), that auth is required, and the specific 404 error codes returned. This is exactly the kind of side-effect disclosure a destructive tool needs.

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-loads the use case, then what gets deleted, then the inputs, return shape, and errors in a tight sequence. The 'Inputs:' sentence largely repeats the schema so a small amount of space is not strictly earned, but the overall density is high.

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?

With no output schema, the description supplies the return shape ({id, deleted:true, messages_deleted}) and the failure modes (thread_not_found, inbox_not_found), so an agent has everything needed to invoke and interpret the call. Complete for a two-parameter destructive tool.

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 both parameters are already documented in the schema. The description restates them, including the accepted inbox_id formats, adding only marginal value over the structured data; baseline 3 applies.

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 ('Deletes every message in the thread') and precisely scopes the operation as removing a whole conversation. It is clearly distinguishable from siblings like cooper_delete_inbox, cooper_delete_draft, and cooper_delete_list_entry.

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?

'Use this when a whole conversation should be removed' gives a clear triggering condition and implicitly frames the granularity (whole thread vs. individual items). It does not name an alternative tool or state when NOT to use it, and no sibling delete-message tool exists to route to, so this is clear context without explicit exclusions.

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