discover_merchant

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

With no annotations provided, the description carries the full burden. It discloses the network fetch behavior, the returned data categories, and the side effect of registering the merchant. It does not cover failure modes or persistence details, but is transparent enough for a simple discovery operation.

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, with the core action and output front-loaded. Every sentence contributes meaningful context.

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 tool, the description covers what it does, what it returns, and the registration side effect. It could mention error behavior for non-UCP-enabled merchants, but the provided information is sufficient for an agent to invoke it correctly.

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 parameter-level detail beyond what the schema already provides for the 'url' parameter, but the schema already explains the base URL format and provides an example.

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 states a specific action ('Discover a UCP-enabled merchant'), the mechanism (fetching the /.well-known/ucp profile), and the expected output (capabilities, services, payment handlers). This clearly distinguishes it from the product-focused sibling tools like search_products and get_product.

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 usage as a prerequisite: 'The merchant is registered for subsequent search and lookup operations.' This tells the agent when to call it relative to sibling tools, though it does not explicitly name alternatives or state when not to use it.

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