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

readOnlyHint=true already tells the agent this is a safe read, so the description's burden is light. It adds a page size mention ('100 per page') but that duplicates the schema's limit maximum/default rather than disclosing new behavior, and says nothing about what the response returns beyond paging.

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?

A single front-loaded sentence that identifies the action, the scope, the dependency (list_groups) and the page size without any filler.

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 a fully documented schema and annotations, the description covers what is needed; the only mild gap is that the response shape (e.g. next_start) is only implied via the start parameter's schema text.

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 group_id (UUID pattern), limit (1-100) and start ('use next_start from the previous reply') are already fully documented. The description adds no syntax or constraint beyond restating pagination, making baseline 3 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?

Specific verb (List) plus resource (contacts that belong to one contact group) with clear scope, and it points at dialmycalls_list_groups as the source of group ids, which separates it from the sibling dialmycalls_list_contacts.

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 parenthetical '(from dialmycalls_list_groups)' tells the agent how to obtain the required group_id, and 'one contact group' clarifies the tool is group-scoped. It stops short of explicitly contrasting with dialmycalls_list_contacts for a flat listing.

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