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

Annotations already cover the safe read-only/idempotent profile, and the description adds meaningful behavior: newest-first ordering, inclusion of missed calls with reasons, assistant confirmation calls, and the left_message field for low-balance missed calls. It does not explicitly describe pagination behavior even though the schema has a 'before' parameter.

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 purpose and ordering are front-loaded, and most sentences add concrete behavioral detail. Some low-balance left_message detail is niche, and the final 'Free.' fragment is terse, but the description remains reasonably efficient.

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?

With no output schema, the description usefully explains what is returned: who, when, duration, cost, missed-call reasons, and assistant confirmation calls. It is strong on return content and special cases but still leaves gaps around the limit and include_missed parameters.

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 only 33%, with only 'before' documented in the schema. The description explains ordering and that missed calls are included, which gives useful context for include_missed, but it does not explicitly explain limit or the include_missed toggle, so it only partially compensates for the low schema coverage.

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 specific verb and resource: listing calls to and from the business's numbers, newest first. It distinguishes this listing behavior from the sibling phone_get_call by telling the agent to use that tool to 'Read a whole conversation.'

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 clearly indicates this is the list view for calls and points to phone_get_call when a whole conversation is needed. It does not address other plausibly related siblings such as account_list_calls, but the primary alternative is named.

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