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

Beyond annotations, the description adds meaningful behavior: results are 'immutable preparation terms', failures are 'typed refusal's, and payment material is categorically rejected from model-authored arguments. These traits are not already disclosed by readOnlyHint, openWorldHint, idempotentHint, or destructiveHint, so the description adds real value without contradicting annotations.

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 sentences with no filler. The core purpose and primary safety constraint are front-loaded, and every phrase earns its place. The description is compact while avoiding tautology.

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?

Although the output schema exists and annotations cover safety, the tool has a complex 9-parameter input schema with zero parameter documentation both in the schema and the description. The description also omits when-to-use guidance relative to siblings. For a tool this intricate, the missing parameter semantics make the definition incomplete for reliable invocation.

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 0%, so the description carries full responsibility for explaining the 9 parameters, but it does not. The only parameter-related clue is the payment-material restriction, which implicitly touches the 'input' field. The remaining parameters — offer_id, offer_revision, digests, canonicalizer_version, idempotency_key, parent_binding — receive no semantic explanation, leaving a major gap.

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?

Description states a specific verb ('Validate'), a specific resource ('one exact invocation envelope'), and the outcome ('return immutable preparation terms or a typed refusal'). This clearly distinguishes it from sibling tools like cancel, get, or search, and the payment-material constraint adds further operational specificity.

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 description implies the tool is for validation/preparation of an invocation and warns that payment material must never come from model-authored arguments. However, it never explicitly states when to use this tool versus siblings such as ausca_get_offer or ausca_get_invocation, nor does it name alternatives or exclusion conditions. Usage context is present but inferred rather than explicit.

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