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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and non-openWorld, so safety behavior is covered. The description adds that a single-call fetch includes recording details and that listings surface transcripts, which is useful content context, but says nothing about ordering, pagination beyond the schema's limit hint, or volume characteristics.

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 tight sentence with the list mode front-loaded and the alternate mode after it. No filler, nothing repeated from the schema.

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 read-only list tool with full annotation coverage and no output schema, the description covers both modes and the notable returned content. The one meaningful omission is the `contactId` filter, which an agent would have to infer from the bare parameter name.

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 75% and the schema already documents `id`, `limit`, and `voicemailOnly`; the description reinforces `id` and voicemail transcript retrieval but adds no syntax or format detail. Critically, `contactId` is undocumented in both schema and description, leaving a real gap.

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?

Names a specific verb and resource ("List call history") and enumerates the fields it returns (direction, duration, voicemail transcripts), plus the dual mode of fetching a single call by id. It is clearly distinguishable from most siblings by resource, though it does not explicitly contrast with adjacent list tools like voicemail_drops_list or activity_list.

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 two modes are stated (list vs. fetch one by `id`), which implies when each applies, but there is no explicit guidance on when to prefer this over sibling listing tools, no prerequisites, and no statement of what happens with no arguments.

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