lookup_reason_codeLook up one card-network chargeback reason code: what it means, the evidence that wins the representment, the response window, and the full guide URL. Accepts the code (e.g. '13.2') or a slug fragment (e.g. 'visa-13-2').
| Name | Required | Description | Default |
|---|---|---|---|
| query | Yes | Reason code like '13.2' or '4515', or slug fragment like 'visa-13-2' |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden; it does disclose the payload contents (meaning, evidence, window, URL), which is real value. It omits behavioral edge cases that matter here — whether a slug fragment can match multiple codes, what happens on a miss, and whether the lookup is cached/rate-limited. 'Look up' implies a safe read but that is never confirmed.
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?
Two sentences, no filler, and the return contents are front-loaded before the input forms. Every clause earns its place.
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 one-parameter read-only lookup with no output schema, the description is close to sufficient because it enumerates the returned fields. The remaining gap is ambiguity handling for fuzzy slug fragments and a nudge toward list_reason_codes for browsing.
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 coverage is 100% and the single parameter already documents both accepted forms with identical examples ('13.2', 'visa-13-2'). The description restates the schema's examples rather than adding new meaning (e.g., normalization rules, partial-match behavior), so the 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?
States a specific verb (look up) and a precisely scoped resource (one card-network chargeback reason code), then enumerates exactly what comes back: meaning, winning evidence, response window, guide URL. The singular 'one' implicitly separates it from the sibling list_reason_codes, so an agent can pick it without opening either schema.
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?
Usage context is only implied: 'one' code suggests a targeted lookup versus the sibling list_reason_codes, but the description never says when to use this instead of listing or get_response_deadlines. No prerequisites or exclusions are stated, leaving the agent to infer routing.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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