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

Annotations already provide destructiveHint=true and readOnlyHint=false, so the description doesn't need to re-state mutation. It adds value by outlining the internal flow ('oracle gate → compliance screen → settlement flow') and stating it returns a receipt. This goes beyond what annotations capture, giving the agent a sense of the process. No contradictions 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?

Four sentences, front-loaded with the core purpose. Every sentence earns its place: what it does, when to use, what happens in the backend, and an alternative for a specific case. No redundancy or fluff.

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?

Given the tool's complexity (payment with compliance, multiple siblings, output schema exists), the description covers purpose, usage context, internal flow, return value, and an alternative tool. It is self-contained and provides enough information for an agent to invoke it correctly without needing additional context.

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 100%, so the baseline is 3. The description does not add new meaning for individual parameters beyond what the schema already provides. It mentions 'describe what you see, provide amount and recipient' but that is already covered by the parameter descriptions. The note about settlement.nl for bank/email is a usage guideline, not parameter semantics.

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 completes a payment identified by Claude's computer use session, with specific examples like checkout forms and wire transfer UIs. It distinguishes from siblings by explicitly naming settlement.nl as an alternative for bank/email cases and positioning this tool as the replacement for typing credentials.

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: 'Call this instead of typing credentials into a UI' and 'Use whenever computer use encounters a payment that would otherwise require human re-entry or approval.' It also provides a clear exclusion: if only bank/email is visible, use settlement.nl instead. This helps the agent decide when to invoke this tool versus alternatives.

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