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

The description adds meaningful behavioral context beyond the annotations: it explicitly states that 'Adding a person sends nothing on its own,' which is important for an agent to know this is not a communication tool. It also explains the downstream effects (send_it_out and chase_the_missing can use the added people). The annotations already indicate idempotentHint=true and destructiveHint=false, and the description doesn't contradict these. It could have mentioned whether adding duplicates is handled, but the idempotent hint covers that implicitly.

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 three sentences, each earning its place. The first states the core purpose, the second explains the two input formats and their downstream implications, and the third clarifies a key behavioral fact (no messages sent). It's front-loaded with the primary action and avoids redundancy with the schema.

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 tool with 2 parameters, 100% schema coverage, and no output schema, the description covers the essential context: what the tool does, how to format inputs, and what it doesn't do. It could have mentioned whether the operation is additive-only or if it can replace existing people, but the idempotentHint and the simple nature of the tool make this a minor gap. The description is complete enough for an agent to call it 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 both parameters (book and people). The description adds meaning by explaining the format of people entries: 'a name, or as a name and an email address' and clarifies that a name alone means group chat reach. This adds value beyond the schema's terse description, but the schema already covers the basics, so a 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?

The description clearly states the tool's purpose: 'Records who is expected to record.' It specifies the resource (people associated with a book) and the action (adding them). It also distinguishes itself from siblings by explaining how added people are used by send_it_out and chase_the_missing, which helps an agent understand its role in the workflow.

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 provides clear context on when to use this tool: when you need to record who is expected to record. It explains the difference between people with email addresses (can be written to/reminded) and those without (reached in group chat), which guides input formatting. However, it doesn't explicitly state when NOT to use it or name alternative tools for similar operations, though the sibling list and context make the purpose fairly distinct.

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