Mark Folder Read

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

Annotations cover the safety profile (readOnlyHint=false, idempotentHint=true, destructiveHint=false), and the description adds genuinely useful behavioral context beyond them: the per-call cap of max_messages, the need to loop while remaining_unread > 0, and the routing hint to m365_update for single messages. It does not spell out permission requirements, but the operational loop semantics are the key disclosure an agent needs here.

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 short sentences, front-loaded with the core action and scope, followed by the iteration rule and the sibling routing. No filler or redundant restatement of the name.

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 (including remaining_unread) need not be explained, and the description references the field that drives the loop. Together with the annotations covering mutation safety and idempotency, an agent has everything needed to invoke and re-invoke this tool correctly.

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 folder_id, account_id, and max_messages are all fully documented in the schema. The description only echoes max_messages' role as a per-call cap without adding format or constraint detail beyond the schema, so the 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 (mark as read), resource (every unread message in one mail folder), and scope (bulk, folder-wide) in the first clause. It also explicitly distinguishes itself from m365_update for single-message operations, so an agent can differentiate 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?

Gives a clear iteration rule ('If remaining_unread is above zero, call again') and names the alternative for single-message edits (m365_update). It lacks explicit when-not-to-use guidance for the tool as a whole (e.g., preferring search-based filtering), but the batching contract is well communicated.

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