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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the agent knows this is a safe, pure, repeatable read operation. The description adds the cost (0.003 USDC), which is useful operational context not present in annotations. However, it does not describe output format, detection sensitivity, or how duplicates are identified.

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 a single, efficient sentence that front-loads the purpose and appends the cost. It wastes no words, though it could be slightly more structured by separating purpose and cost.

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 single-parameter read-only detection tool with no output schema, the description covers what is detected and the cost. However, it lacks details on input format, output shape, and when to use it, which are needed for correct invocation given the 0% schema description coverage.

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 0%, so the description must carry the burden of explaining the 'charges' parameter. The description mentions 'transaction hashes, payment identifiers and idempotent intents', which hints at what the charges array should contain, but does not specify the expected object shape, required fields, or limits (maxItems: 1000 is only in the schema). This leaves a significant gap for the sole required parameter.

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 names a specific verb (detect) and resource (duplicate/repeated transaction hashes, payment identifiers, idempotent intents). It clearly distinguishes itself from adjacent siblings like payment_preflight and idempotency_replay_guard by focusing specifically on duplicate detection. However, it does not explicitly differentiate itself from payment_diagnose or payment_receipt_reconciler.

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?

There is no guidance on when to use this tool versus alternatives. The description does not mention prerequisites, when-not-to-use cases, or which sibling tools handle related concerns. The only contextual cue is the cost, which helps with selection but is not usage guidance.

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