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

Annotations already declare non-readOnly, idempotent, non-destructive. The description goes beyond them by disclosing the side effect (messages stop arriving), the cost of omission (unacknowledged messages repeat on every response), and the return value (messages still pending). Adds real behavioral 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?

Three tight clauses, front-loading the purpose and effect before the how-to. Every sentence earns its place, though the trailing return-value sentence is slightly separable.

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 a mutating tool with no output schema, the description covers the trigger, the effect, the repeat penalty, and the return value. Complete enough to call correctly; only the repo_id source is left entirely to the schema.

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 both ids and repo_id are already documented. The description's 'ids from messages_pending' largely restates the schema's own id description and adds no format/syntax detail. Baseline 3 is appropriate.

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 handled) and resource (messages from teammates' agents), and names the concrete effect (so they stop arriving). An agent can tell this apart from siblings like send_agent_message or recall 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?

Gives clear triggering condition: 'pass the ids from messages_pending once you have acted on them.' The repeat-on-every-response note reinforces when it must be called. No explicit when-not or named alternative, but the context is unambiguous.

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