Update a price

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

Goes well beyond the annotations by disclosing field-level update semantics: `refunds` is replaced wholesale with omitted subfields reverting to defaults, `metadata` is merged (empty value deletes a key), and amount/model are immutable. It also flags the environment gate (test keys only), which is exactly the kind of operational constraint an agent cannot infer from structured data.

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 tight sentences, front-loaded with the editable field list before the constraints. The middle sentence is a telegraphic fragment ("Nickname, active, refund terms ... and metadata.") that reads as terse rather than wasteful.

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?

Covers the mutation semantics, immutable fields, and key restriction for a 5-parameter tool with a nested object and no output schema. It does not describe the response shape, but nothing critical for invoking 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?

At 60% schema coverage the description adds real value by explaining the differential semantics of the updatable fields (whole-replacement vs. merge) that the schema only partially documents for `metadata` and not at all for `refunds`. The phrase "what you leave out takes its default" is slightly ambiguous about whether it applies to the refunds object or its subfields, but the intent is recoverable.

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?

Specific verb + resource ("Update a price") that is unambiguous against siblings like create_price, list_prices, or update_product. It does not explicitly name an alternative, but the resource noun does the differentiating work.

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 concrete exclusion boundaries: amount and pricing model cannot be changed here, and all calls must use a test key (live keys are refused). It stops short of naming an alternative tool for changing amounts, but the eligibility constraint is clear enough to route correctly.

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