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

Beyond the readOnly/idempotent annotations, it discloses non-obvious behavior: results omit the body, the list can go stale because the user can edit/save/send in the draft editor card with no notice, and reply drafts return untrusted_content: true. Pagination via limit (max 50) is implied. This is exactly the kind of context annotations cannot carry.

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 purpose, then return shape, then the ID handoff, then the staleness caveat. Dense with useful content and no filler, though the staleness/untrusted-clause sentence is somewhat convoluted and could be split or trimmed.

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 a full schema, an output schema, and annotations, this covers everything an agent needs: what comes back, what does not (body), how to get it (draft_read), how IDs chain to write tools, and the freshness caveat.

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 inbox, inbox_id and limit are already documented in the schema. The description adds no syntax or defaulting guidance for them, and its only ID discussion (draft_id) concerns results, not inputs. 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?

Opens with a specific verb+resource and scope: 'Return draft messages saved in the inbox's Drafts folder.' It immediately contrasts with the sibling draft_read ('no body: draft_read returns one draft's text'), so an agent can tell the list tool apart from the single-draft reader without opening either schema.

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?

Routes clearly: use this to enumerate drafts, use draft_read for a body, and the returned draft_id feeds draft_read and draft (action 'update'/'send'/'delete'). It also warns the user may mutate drafts outside the tool, implying a re-read via draft_read. It does not explicitly exclude use for searching (e.g., email_search_and_move), which is the only gap.

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