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

Annotations already flag readOnlyHint=false, idempotentHint=true and destructiveHint=true, so the safety profile is partly covered. The description adds provenance requirements ('valid receipt pairs from a retrieved batch') and a semantic boundary ('retrieval does not claim understanding, action or an answer'), but never explains what the destructive marking actually does – whether messages leave the inbox, whether receipts become unusable, or how partial batches behave.

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 action and protocol method, then the precondition, then the semantic caveat. No filler, though the final sentence is a caveat rather than invocation guidance.

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?

For an idempotent-but-destructive mutation with no output schema and zero schema documentation, the description covers intent, provenance and semantic scope but omits the consequence of acknowledgement, error/partial-success behavior, and whether the operation is revocable.

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%, so the description must carry the load. It describes the paired nature of the data ('exact returned sequence/receipt pairs') and hints at client scoping ('by this client'), but adds no detail on format, limits (max 100), uniqueness, or what identifies a valid pair beyond what the raw schema already shows.

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?

Names a specific verb and resource: 'mark ... as retrieved by this client (inbox:ack)', plus the exact input shape (sequence/receipt pairs). It implicitly separates itself from the read-side sibling (check_inbox) by requiring pairs 'from a retrieved batch', though it never names that alternative explicitly.

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?

States a clear precondition – the pairs must come from a retrieved batch and be valid – which tells the agent when this tool is callable and that it must not be called on arbitrary data. It stops short of naming check_inbox as the source or saying when acknowledgement is unnecessary/optional.

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