Vendor costs and hours

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

With readOnly/idempotent/openWorld annotations already covering the safety profile, the description adds real behavioral context: coupons are unavailable, open_now is the live site state, any status other than 'Open' (including OutOfCoverage = no delivery to this point) makes it false, and eta_max means 'up to N minutes'. These are non-obvious semantics an agent could not infer from the annotations or schema alone.

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?

Front-loaded with the returned fields, then the usage rule, then edge-case semantics, with no filler sentences. It is dense but every clause carries information (cost formula, min_order requirement, coupon gap, status/ETA semantics), so the length is justified rather than padded.

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?

There is no output schema, and the description compensates by enumerating the returned fields and explaining the non-obvious ones (open_now, eta_max, status states). An agent has enough to call it and interpret the result correctly, with only minor gaps around response ordering/shape.

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%, so the baseline is 3, but the description adds meaning the schema does not: lat/long are the delivery *point* whose value changes the delivery fee and coverage result, and vendor_code flows from tf_search_vendors / tf_restaurants. That clarifies the interdependency between the coordinate pair and the returned fee rather than merely restating the params.

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 and resource ('Get a vendor's delivery fee to a point, minimum order, packaging, ETA, open_now, hours, address and rating spread'), enumerating exactly what comes back. This distinguishes it from search-oriented siblings like tf_search_vendors, tf_restaurants, or tf_menu, which return lists rather than a single vendor's delivery economics.

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?

'Use before recommending a vendor: true cost = dish price + packaging + delivery_fee, and the basket must reach min_order' gives a clear triggering condition and the decision rule the agent should apply. It also rules out a false expectation ('Coupons are not exposed'), steering the agent elsewhere for deals. It stops short of naming an explicit alternative tool or a when-not-to-call case.

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