Sync mail into the vault

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

Beyond the annotations (idempotentHint, destructiveHint), the description adds rich behavioral detail: cursor-based resume per provider+mailbox, UIDVALIDITY reset handling with a response signal, and the dry_run mode. These details tell the agent exactly what to expect regarding statefulness and side effects without contradicting the annotations.

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?

Four sentences with zero filler. The core purpose is front-loaded in the first sentence, followed by essential behavioral distinctions, idempotency, resume mechanics, and the key invocation hint for dry_run. Every sentence earns its place.

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 an output schema present, return values need no explanation, and the description covers side effects, idempotency, cursor behavior, and dry_run. The only noticeable gaps are the meanings of days, limit, and apply_smart_filter, which are not obvious for an agent making a fully informed call. Still, the operational context is strong enough for correct selection and generally correct invocation.

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 0%, and the description compensates for only one parameter: dry_run ('Set dry_run=True to see paths without writing'). The mailbox parameter is mentioned indirectly via 'per provider+mailbox', but days, limit, and apply_smart_filter remain entirely unexplained. This is insufficient for a 5-parameter tool with no schema descriptions.

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?

The description opens with 'Write mail into the second brain as markdown notes', giving a specific verb, resource, and output format. It further distinguishes itself from all siblings by stating it is 'the only tool here that writes anything', making the purpose unmistakable and differentiating it from the read-only imap_* tools.

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?

The description clearly states this is the only tool that writes, which implies its use case is vault-writing rather than reading or searching. It also clarifies it never modifies the mailbox. It does not explicitly name sibling alternatives or exclusions, but the 'only tool here that writes anything' phrasing provides strong routing guidance.

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