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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds value beyond that by disclosing that response groups are group names even though the API stores IDs, meaning the tool performs resolution internally. The explicit 'Side effects: none' line is redundant with annotations, but the group-resolution detail earns credit.

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 compact and front-loaded with the core purpose, followed by filtering guidance, workflow context, and output behavior. Every sentence earns its place and there is no filler or repetition.

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 an 11-parameter read-only list tool with an output schema and strong annotations, the description covers filters, pagination, sorting, shared/personal scope, group resolution, and integration order. Nothing critical is missing for an agent to invoke 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 coverage is 100%, so the baseline is 3, but the description adds practical meaning with examples like name=Jane, clarifies pipeline_id usage in the fax workflow, and explains group-name resolution. These go beyond the schema's individual parameter descriptions without contradicting them.

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 resource (contacts) and the specific capabilities: optional filters, pagination, sorting, and shared/personal filtering. This distinguishes it from sibling list tools like list-numbers or list-contact-groups without needing to inspect schemas.

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?

It explicitly instructs agents to use server-side filters rather than fetching everything and filtering client-side, and provides a concrete fax-workflow ordering: call after pipeline_start and list-numbers, before request-file-from-user. It also tells the agent not to ask the user for a contact, which is a strong guardrail against tool misuse.

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