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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is well covered. The description's 'Side effects: none (read-only)' merely restates those annotations and adds no new behavioral context such as result-scope semantics, sharing behavior, or pagination implications. No contradiction exists, but no value is added beyond the structured hints.

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 short and front-loaded: the first sentence gives the purpose and capabilities, and the second adds a safety note. It is economical, though the second sentence is somewhat redundant with the annotations. Overall it is well-structured and free of 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?

For a simple read-only list tool with an output schema, fully described parameters, and robust annotations, the description is sufficient for an agent to invoke it correctly. It could be more explicit about result scope or the distinction between shared and personal groups, but those details already exist in the schema, so the description is not critically incomplete.

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%, with each of the five parameters already explained in the input schema. The description's mention of 'optional pagination and filters' is generic and does not add meaning beyond what the schema provides. Baseline 3 is appropriate because the schema carries the semantic load.

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 states a clear verb and resource: 'List contact groups' and adds the domain clarification '(Fax.Plus tags)'. It also mentions optional pagination and filters, which goes beyond a bare tautology. It does not explicitly differentiate from sibling tools like list-contacts, but the resource is specific enough that the purpose is unambiguous.

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?

There is no guidance on when to use this tool versus alternatives such as list-contacts, create-contact-group, or update-contact-group. The description only lists capabilities ('optional pagination and filters') and notes read-only side effects, but does not explain when an agent should choose this tool or what exclusions apply.

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