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

Goes well beyond the annotations by disclosing inherited behavior from call_person: content screening, verified Caller ID, a daily cap, a strict no-platform-number-fallback policy, no-answer retry decisions, and idempotency rules. It does not spell out what 'destructiveHint' means for this specific action (e.g. whether a placed call can be cancelled), so it is strong but not exhaustive.

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?

Front-loaded with the core action and the constraint, then the required sequence, with every sentence carrying a distinct instruction. The closing references to call_person's retry and idempotency rules are slightly indirect but still useful and compact.

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 nine-parameter, externally-effecting call tool with an output schema, the description covers prerequisites, confirmation gating, safety policies, and retry/idempotency inheritance. Nothing essential to invoking it correctly is missing, and return values are legitimately left to the output schema.

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 all nine parameters are already documented, and the description mainly restates the contact_ref/user_confirmed relationship the schema carries. The added nuance (re-list and re-confirm if the contact changed before dialing) is really workflow guidance rather than parameter meaning, so the baseline 3 fits.

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?

States a precise verb+resource ('Call a saved private contact') and immediately carves out scope versus the number-based sibling with 'without passing their full number.' An agent can distinguish it from call_person and call_business without opening any schema.

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?

Gives an explicit ordered workflow (list_contacts first, confirm name/masked number/message, then pass contact_ref and user_confirmed=true), a pre-flight check (caller_id_status), and a re-confirmation condition if the contact changes. Alternatives and prerequisites are named rather than implied.

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