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

With no annotations, the description carries the full burden of behavioral disclosure. It reveals a key non-obvious behavior: retrying without an idempotencyKey will cause duplicate payments. This is a concrete, actionable trait that goes beyond the bare 'pay' statement, though it does not fully describe other side effects like reversibility or error responses.

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 exactly two sentences: the first states the core purpose, and the second front-loads the critical idempotency warning. Every word earns its place, with no fluff or repetition.

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 financial tool with 6 parameters, no annotations, and no output schema, this description is under-specified. It omits what 'from' and 'to' refer to, whether asset is required or defaulted, the purpose of reference, and the success/error return shape. The idempotency note is valuable but does not make the tool safely usable by an agent without further inference.

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 17%, so the description must compensate for the other parameters. It meaningfully explains only idempotencyKey; it does not clarify the semantics of to, from, asset, or reference. The purpose statement implies from/to but fails to specify their format or relationship, leaving agents to guess.

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 'Pay another agent directly' uses a specific verb and resource, clearly identifying the tool's function. It distinguishes from sibling tools like withdraw (self-payment) and advance_credit by emphasizing 'another agent' and 'directly', making the purpose unambiguous.

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 description gives a critical usage guideline: 'Always pass an idempotencyKey' with a clear rationale about double payment on retry. While it does not mention alternative tools or when not to use it, the explicit 'always' instruction and failure-mode explanation provide strong practical guidance.

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