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

Annotations already cover the safety profile (readOnly=false, idempotent=true, destructive=false, openWorld=false), so the bar is lower. The description still adds real value by disclosing the actor constraint ('only the opposite side') and clarifying that acknowledgement is not task completion ('does not imply task success') — semantics the annotations cannot express.

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?

Two short sentences with zero filler; the core action is stated first and the two constraints follow. 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?

The annotations plus the actor and non-success caveats give an agent enough to call it safely, and no output schema exists to explain. But for a five-required-parameter mutation with an idempotency key and a version precondition, the description leaves the calling contract under-specified.

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% across five required parameters, so the description must carry the meaning. It only touches the receipt parameter implicitly ('delivered or read') and says nothing about expected_message_version (optimistic concurrency), idempotency_key, or the message/conversation id formats — a significant gap for a mutation with an idempotency contract.

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?

Specific verb (acknowledge) plus resource (conversation message) with the receipt values named, so the operation is unambiguous. It implicitly contrasts with send_conversation_message but never names a sibling to differentiate from it, so it stops short of a 5.

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 clause 'Only the opposite side can acknowledge' is a genuine caller precondition, which is more than most definitions offer. However, there is no guidance on when to use this versus related tools such as respond_to_request or complete_conversation_draft, and no explicit exclusion conditions.

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