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

With annotations already carrying read-only, idempotent, and non-destructive hints, the description adds meaningful behavioral context: results are ordered most recent first, and the response includes specific fields. This goes beyond the schema and annotations without contradicting them.

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 description is short and front-loaded: the primary action is in the first two words, followed by field information and ordering. Every sentence is useful with zero filler or redundancy.

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 simple list call with two optional parameters and no output schema, the description supplies the output field names, ordering, and overall scope. The schema documents the limit and status filters, so nothing needed for correct invocation is missing.

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 descriptions cover 100% of the parameters (limit and status), so the parameter semantics are already fully captured in the schema. The description does not add new parameter meaning, but it also doesn't need to; a baseline 3 is appropriate.

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 clearly states the action ('List recent calls') and the resource (call history), with useful specifics about included fields (status, duration, cost) and ordering. It does not explicitly mention sibling tools, but the verb 'list' and phrase 'recent calls' make the distinction from get_call/get_usage apparent.

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 intended use is implied: call this when you want a list of recent calls. However, there is no explicit guidance about when to prefer get_call for a single call or get_usage for aggregated usage, and no alternatives are named. This is adequate but leaves some routing to the agent.

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