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

Annotations already declare idempotentHint=true, destructiveHint=false, readOnlyHint=false and openWorldHint=true, so the safety profile is covered. The description adds beyond them: preparation terms are immutable, failures surface as a 'typed refusal', and payment material is rejected from model-authored arguments - meaningful behavioral context an agent cannot read off the annotations. It still omits auth/permission requirements.

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, zero filler, and the outcome (terms or refusal) is front-loaded before the security constraint. Nothing is redundant with the title or schema.

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 7-required-parameter, 0%-coverage mutation-adjacent tool, the description leaves an agent unable to determine where offer_id, offer_revision and the schema digests come from or when this call must precede another. The output schema existing means return values need no explanation, but the input-side gap is serious.

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?

All seven required parameters have 0% schema description coverage; the schema only supplies types, patterns and $refs. The description says only that the payload is 'one exact invocation envelope', which hints that the offer/digest fields bind an exact revision but explains none of offer_id, offer_revision, the three digests, input or idempotency_key.

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 ('Validate one exact invocation envelope') plus the outcome ('return immutable preparation terms or a typed refusal'), which is far more than a restated title. It does not differentiate itself from siblings such as ausca_get_invocation or ausca_cancel_invocation, so an agent must infer where this fits in the invocation lifecycle.

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?

No statement of when to call this versus ausca_get_invocation, ausca_cancel_invocation, or elsewhere in the flow, and no prerequisites. The only boundary given is a prohibition ('never accepts payment material from model-authored tool arguments'), which is a constraint rather than usage routing.

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