Get listing detail

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

With no annotations, the description carries the behavioral burden. It discloses that no API key is required, that the operation is a read-only fetch, and that output includes variants, delivery options, pricing, and a Nano total. It adds practical behavioral guidance by telling agents to use the Nano total as quotedTotalNano to guard against exchange-rate drift.

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?

Three sentences, each carrying distinct value: core action, authentication requirement, and output/usage guidance. The description is front-loaded and contains no filler or redundant restatement of the tool name.

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 tool with no output schema, the description is complete enough. It covers what the tool returns, the auth context, and how the return value should be used downstream. The input origin is documented in the schema, so no critical context is missing.

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 already provides full 100% coverage for listingId, including its format and source. The description only says 'by ID' and does not add parameter-specific meaning beyond the schema. Baseline 3 applies because the schema does the heavy lifting.

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 uses a specific verb ('Fetch') and resource ('a single listing by ID'), clearly distinguishing it from search_listings. The title reinforces the same purpose. An agent can tell exactly what this tool does without ambiguity.

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 implies the tool is used after search_listings by noting the listingId comes from search_listings in the schema, and it connects to the purchase flow. It provides clear context but does not explicitly name alternatives or when-not-to-use conditions.

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