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

Annotations already declare readOnlyHint=true, and the description reinforces it with 'Read only: nothing is booked', removing any doubt that this is a quote rather than a booking. It also discloses the response shape (fee, pickup/delivery time, durations, per-service errors) and that the data comes from third-party services, adding real context beyond the annotation.

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 tight sentences: the capability and return contents first, then the read-only reassurance and endpoint. Every clause earns its place with no redundancy.

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-param read tool with no output schema, the description supplies both the prerequisite (existing order) and the returned fields, including per-service errors. Nothing an agent needs to invoke or interpret it correctly 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?

With 100% schema description coverage on the single order_id parameter, the schema already carries the semantics, including the important distinction from the order number. The description adds nothing about the parameter, so the baseline 3 applies.

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 fee and time estimates ... for an existing order') and enumerates the returned fields, which cleanly separates it from siblings like shipday_get_on_demand_details and shipday_check_on_demand_availability. An agent can select it without opening the 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?

The prerequisite is explicit – it requires an 'existing order' and reads Shipday's GET /on-demand/estimate/{orderId}. It gives clear context for use but names no exclusions or alternative tools (e.g., when to prefer check_on_demand_availability).

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