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

The description adds the statement 'Side effects: creates contact group,' which explicitly discloses the non-read-only nature. Annotations already set readOnlyHint=false and destructiveHint=true, so the description does not contradict them (though 'destructive' is a misnomer for creation). The description provides no additional behavioral context like permissions, reversibility, or impacts on existing data, so it offers only minimal value beyond annotations.

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 two sentences plus a side-effect note, with zero waste. The purpose is front-loaded in the first sentence, the critical usage nuance follows immediately, and the side effect is stated separately. Every sentence earns its place, making it highly concise and well-structured.

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 tool has an output schema, so return values are covered. However, with three parameters and no parameter descriptions in the schema, the description is incomplete for full correct usage—it omits what 'notes' and 'shared' mean and any constraints on 'name.' The name-vs-id note is valuable but does not address these gaps. Overall, it covers the core purpose but leaves significant parameter semantics uncovered, making it partially complete.

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 compensate for parameter meanings. It only indirectly clarifies the 'name' parameter by noting that the group's name is used for assignments, but it does not explain 'notes' or 'shared' at all. Since these parameters are undocumented in both schema and description, an agent has no guidance on their purpose or constraints. The description fails to carry the burden of explaining parameters.

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 ('Create a contact group (Fax.Plus tag)') and its purpose ('to organize contacts'). It also distinguishes this tool from siblings like update-contact-group and delete-contact-group by the explicit note that when assigning contacts via set-contact-groups / create-contact / update-contact, the group's name (not id) must be passed. This is a specific differentiator that an agent can act on.

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 gives a concrete usage instruction: when assigning contacts, use the group's name rather than its id. This implies when the created group will be consumed and provides a key step for correct integration. However, it does not explicitly state when to use this tool versus alternatives (e.g., list-contact-groups for lookups) or when not to use it. The guidance is useful but incomplete for full routing.

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