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

Annotations only say it is non-read-only, non-idempotent and non-destructive; the description adds the real behavioral context: credential scope, workspace claiming, the 403 refusal path, and that passing agentid_token causes the caller to be recorded as a verified buying agent. It doesn't say whether repeated calls create separate quote records (relevant given idempotentHint=false).

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?

The core is front-loaded and the credential/workspace requirements earn their place, but the middle sentence is a flat laundry list of eleven parameter names that duplicates the schema without adding meaning. Trimming that enumeration would tighten it considerably.

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 an 11-parameter, nested-object tool with no output schema, it covers prerequisites, funnel stage, token semantics and a failure mode — enough for an agent to attempt the call correctly. The shape of the returned quote is only loosely implied ('answers a UCP quote').

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 schema already documents every parameter, and the description's opening sentence largely re-lists parameter names. It does add a little: stage defaults to quote and routing_preference applies 'when none is named' — but that is already in the schema descriptions too. 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: prices a cart through the UCP pricing network and returns a UCP quote. It is distinguishable from catalog/compute tools by naming the UCP cart funnel, but it never explicitly contrasts itself with close siblings like compute_price or compute_prices_batch.

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?

Gives clear operating context: needs a Last Price credential with price compute scope and a claimed workspace, and the sandbox-key 403 case is spelled out. There is no explicit 'use this instead of X' routing against compute_price / compute_prices_batch, which keeps it below 5.

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