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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description still adds two non-obvious behavioral facts: results are ordered newest-first, and kind/unread are mutually exclusive arguments. It says nothing extra about pagination beyond what the schema's cursor/limit descriptions already state.

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?

A single 11-word sentence with no filler; the resource is front-loaded and the constraint follows. Every clause carries information.

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 100% schema coverage, four annotations and no output schema, most of the burden is already carried by structured fields, and the description supplies the one missing cross-parameter rule. The remaining gap is disambiguation from the inbox_read/replies_list siblings, which an agent selecting among 29 tools would benefit from.

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 the baseline is 3, but "kind and unread exclude each other" is a cross-parameter constraint that is not expressed anywhere in the schema and prevents an agent from sending an invalid combination.

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 the resource (your messages and notices) and the ordering (newest first), which together make the tool's intent clear despite no explicit verb. It does not differentiate from near siblings such as commons_inbox_read or commons_replies_list, so an agent cannot tell which listing endpoint to pick from the description alone.

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?

"Your messages and notices" implies the inbox-listing use case, but there is no explicit when-to-use statement and no mention of the alternative endpoints (commons_inbox_read, commons_replies_list). The mutual-exclusion note is a constraint, not tool-selection guidance.

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