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

The annotations already declare read-only and idempotent behavior, and the description reinforces this with 'Every call is read-only and idempotent.' It also discloses a key behavioral trait: errors never raise protocol errors but return an error object with instructions, ensuring the agent knows how to handle failures. No contradiction with 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?

The description is succinct: three sentences covering purpose, usage guidance, and error behavior, plus a compact example. It is front-loaded with the primary function and every sentence adds substantive value with no 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?

The tool is moderately complex with five parameters and an output schema, but the description fully compensates: it includes an example, clarifies limitations (fees depend on plan/country/card mix), and explains error handling. Since an output schema exists, return values need not be detailed, but the example provides a concrete illustration, making the tool self-contained.

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?

The schema provides 100% coverage for all five parameters. The description adds a concrete example showing how parameters combine (e.g., order_total, fee_pct, fee_fixed, orders, refund_rate_pct) and the expected output shape, which clarifies the semantic interplay beyond the schema's individual field descriptions.

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 tool estimates the net payout after processing fees, using a specific verb (estimate) and resource (net payout). This distinguishes it from the unrelated sibling tools by focusing on financial modeling rather than bulk operations or metafields.

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?

Explicit guidance is provided: 'Use for cash-flow planning' and 'Not as an authoritative fee schedule' with advice to 'pass your own' rates. This tells the agent when to use it and when not to rely on it, addressing usage context and limitations.

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