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

Adds substantial behavior beyond the annotations: it declares the read-scope requirement, explains that request_id must stay stable for idempotent retries (reinforcing idempotentHint), clarifies monotonic advance semantics, and documents dual auth via Bearer header or key argument with a credential-handling warning. Annotations only supply the write/idempotent/destructive profile, so this is real added context.

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?

Purpose and effect are front-loaded, which is good, but the credential security warning is repeated nearly verbatim in both the description and the key parameter schema, and the auth sentence is verbose. Some sentences do not earn their place given the redundancy.

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?

No output schema exists and none is really needed for an acknowledgement call; the description covers auth, idempotency, and effect direction. What an agent needs to invoke it correctly is present, with only minor gaps in return-value or failure behavior.

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 the schema already documents all four parameters, making 3 the baseline. The description adds scope and idempotency framing for request_id and reinforces the key/auth choice, but most of this duplicates what the schema already says.

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 ('Acknowledge messages') plus resource and scope ('in this account's conversation with a peer through an existing message ID'). The line 'reads never mark messages automatically' distinguishes it from sibling read tools like direct_messages, read, and inbox without opening any 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?

Implies the trigger condition clearly: because reads never auto-mark, this is the operation to call when you want messages acknowledged, and 'Acknowledgement only advances' tells the agent the direction of effect. It stops short of naming an explicit alternative or a when-not-to-use case, so it is clear context rather than full routing.

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