acknowledge_message

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

Beyond the annotations (readOnly, idempotent and destructive all false), the description discloses non-obvious behavior: repeated calls preserve the first read/acknowledge timestamps but refresh the agent's activity time, the sender sees the acknowledgement in get_message_delivery_receipt, ack_overdue_only stops listing it, and it fails with NOT_FOUND unless the caller is a recipient. That is far more than the structured fields provide.

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?

It is dense but every sentence earns its place: purpose and returns first, then repeated-call semantics, then when-to-use, then downstream effects, then the sibling alternative and failure mode. No filler or 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 no output schema, the description compensates by naming the returned fields (message_id, acknowledged, acknowledged_at, read_at). It also covers prerequisites, side effects on other tools, and the failure condition, so an agent has everything needed to invoke it 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 all three parameters are already documented in the schema, and the description adds no format or constraint detail beyond implying recipient status (which relates to the NOT_FOUND failure). Baseline 3 applies when the schema carries the parameter burden.

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 opening sentence names a specific verb and resource ('Acknowledge one received message and mark it read') and even enumerates the returned fields. It is cleanly distinguished from its nearest sibling by the explicit routing sentence 'To mark read without acknowledging, use mark_message_read.'

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 states exactly when to use it ('Acknowledge ack_required mail after acting on it'), what to do otherwise ('if you cannot or will not act, reply with the reason'), and names the alternative tool (mark_message_read) for the read-only case. Nothing is left to inference.

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