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

Annotations already declare the mutation profile (readOnlyHint=false, destructiveHint=true, idempotentHint=true), so the bar is lower, yet the description still adds real context: the read+modify scope requirement, the paid-when-setting / free-when-clearing cost model, and the persistent record plus star/flag side effect. It does not explain the destructive path the annotation implies (the trash-unverified behavior, which only appears in the schema), leaving a small gap.

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?

Three tight clauses pack purpose, lifecycle, and auth/cost into roughly two sentences with the primary action front-loaded. Slightly dense but no filler; 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?

An output schema exists, so return values need not be described. Given that, the description covers side effects, lifecycle, auth, and cost, which is enough to call this correctly. The only omission is any routing against snooze/wake_snoozed, a minor completeness gap rather than a blocker.

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 88%, so the schema already documents account, uid, due, folder, tz, and if_no_reply. The description adds only that clear=true removes the follow-up and that a due date drives the mark, which does not meaningfully exceed the schema. Baseline 3 is appropriate.

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: marks a message to come back to by a date, and also clears it. It even names the storage mechanism (a record in "mailmcp-state" plus a star or flag), which is unusually concrete. It does not distinguish itself from the close sibling snooze, so it falls short of the top mark.

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?

"It resurfaces when list_followups or a scheduled task runs" explains the lifecycle, and clear=true removes it, so the set/clear duality is implied. However, there is no explicit guidance on when to choose this over snooze, which occupies the same conceptual space and is likely the main source of agent confusion.

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