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

Beyond the annotation (destructiveHint: false), the description adds essential behavioral context: the tool is idempotent, will return success when re-acking, and will return 404 for non-existent message ids. This exceeds what annotations provide and fully informs the agent of critical side-effect and error behavior.

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?

The description is exceptionally concise and front-loaded: the first sentence states the core purpose and effect, followed immediately by critical usage and behavioral details. Every sentence serves a distinct purpose with no fluff.

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?

Given the tool's simplicity (one parameter, no output schema, no nested objects), the description is fully complete. It covers purpose, effect, uniqueness, idempotence, and error behavior. An agent has all necessary information to invoke this tool 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 the schema already documents the single parameter. The description adds value by telling the agent exactly where to get the message id (from list_messages or infrastructure_status's messages[]) and that it is a string. A minor deduction because the schema already provides the same relational hint in the parameter description, so the added value is marginal but still helpful.

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 description clearly states the action ('Acknowledge a message by id'), the resource ('message'), and the desired outcome ('sets it read so it stops surfacing as unacked'). It distinguishes the tool from siblings like list_messages and infrastructure_status by emphasizing that only this tool processes the acknowledgment.

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 description explicitly tells when to use this tool ('to set readAt'), what not to rely on instead ('reading or listing messages never marks them'), and critical behavior ('the only thing that sets readAt'). This is exemplary guidance for an AI agent deciding between tools.

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