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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful behavior in the absence of an output schema by enumerating returned fields and stating newest-first ordering, but it omits pagination and default-limit behavior. A moderate contribution given the lower bar set by annotations.

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 leads with the resource and ordering before the field list. It is appropriately sized with no obvious filler, though the field enumeration is long relative to the sparse purpose statement.

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 field list partially fulfills the need to describe return values, but the definition leaves filtering semantics, pagination, and the distinction from get_call unaddressed for a 5-parameter list tool. Adequate but with clear gaps.

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 only 40%: limit and since are documented, while agent_id, direction, and follow_up_only are undocumented in both schema and description. The description names no filtering parameters and does not compensate for the coverage gap, adding nothing to what the schema already says.

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 identifies the resource clearly (voice-agent calls) and the ordering (newest first), so an agent understands it is a listing of calls. However, it uses a noun phrase with no explicit verb and primarily enumerates returned fields rather than stating the action, and it does not differentiate from the sibling get_call. Clear but imperfect.

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?

There is no when-to-use guidance, no mention of alternatives such as get_call for a single call, and no exclusions. The agent is left to infer that a plural 'calls' listing tool is for browsing rather than fetching one record.

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