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

Annotations already declare readOnlyHint=false, idempotentHint=false and destructiveHint=false, so the mutation profile is known. The description adds one genuinely useful trait beyond that - no message is dispatched to the new contact. It omits what happens on a duplicate phone number, which matters given idempotentHint=false.

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?

Two short clauses, both front-loaded: the core action with its hard requirement first, then the no-side-effect assurance. Nothing is wasted.

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 7-parameter creation tool with no output schema and adequate annotations, the essentials are covered: what it creates, what is mandatory, and that nothing is sent. The remaining gap is duplicate handling and whether an id is returned for later update calls.

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 57%, and the description confirms phone is required and group_ids optional, matching the schema. It adds no format or placement detail for email, firstname, lastname or extra1, relying on the schema and self-explanatory names for those.

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 names a specific verb and resource ('Add a contact ... to the contact list') and flags the required field (phone) plus optional group membership. It is clear enough to separate from dialmycalls_update_contact and dialmycalls_send_text, though it never names a sibling explicitly.

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?

'Sends nothing to the contact' implicitly tells the agent this is a data-only operation rather than a messaging one, which is useful routing context. However, there is no explicit guidance on when to create versus update an existing contact, nor any stated prerequisites such as valid group ids.

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