Create a purchase

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

Annotations already declare destructiveHint=true, readOnlyHint=false, idempotentHint=false and openWorldHint=true, so the safety profile is covered. The description earns credit for adding what annotations cannot express: the auth mechanism (OAuth only, no API keys) and the explicit confirm gate, plus a concrete list of affected surfaces (delivery, audience membership, published data, irreversible state). No contradiction with the destructive/irreversible 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?

Three short sentences, front-loaded with the action and immediately followed by risk and prerequisites. No wasted clauses; the only weakness is that 'Create a purchase.' largely restates the title before the useful content arrives.

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 five-parameter, nested-payload mutation with no output schema and no required fields, the description supplies the critical missing context: the confirm gate, OAuth-only auth, and the blast radius. The remaining ambiguity (payload vs. purchase vs. payload_file selection) is handled by the schema's own descriptions, so coverage is adequate.

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 80%, so the schema already documents account, confirm, payload, purchase and payload_file semantics in detail. The description reinforces the confirm=true requirement but adds no syntax, format, or interaction rules beyond that. Baseline 3 is appropriate when the schema carries the load.

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 verb and resource ('Create a purchase') and pairs it with a concrete scope note about what the operation may affect. It is clear, though it never names the sibling reads (get_purchase, list_purchases) that an agent might confuse it with, so differentiation rests on the verb alone.

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?

It gives hard prerequisites ('Requires confirm=true', 'Requires OAuth; API keys are not supported'), which is actionable, but says nothing about when to choose this over list_purchases/get_purchase or what conditions make creation appropriate. Usage is implied by the confirm requirement rather than explained.

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