Ausca

Validate invocation input and return binding terms

ausca_prepare_invocation

Idempotent

Validate one exact invocation envelope and return immutable preparation terms or a typed refusal. Preparation never accepts payment material from model-authored tool arguments.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`input`	Yes
`offer_id`	Yes
`attribution`	No
`offer_revision`	Yes
`parent_binding`	No
`idempotency_key`	Yes
`input_schema_digest`	Yes
`output_schema_digest`	Yes
`offer_revision_digest`	Yes

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 23, 2026

addedInput schema / properties / attribution

Added value: +{
+  "additionalProperties": false,
+  "properties": {
+    "campaign": {
+      "maxLength": 128,
+      "pattern": "^[a-z0-9][a-z0-9._-]{0,127}$",
+      "type": "string"
+    },
+    "source": {
+      "maxLength": 64,
+      "pattern": "^[a-z0-9][a-z0-9._-]{0,63}$",
+      "type": "string"
+    }
+  },
+  "required": [
+    "source"
+  ],
+  "type": "object"
+}

Changed2 schema fields changedSep 18, 2026

removedInput schema / properties / canonicalizer_version

Removed value: -{
-  "const": "runx.receipt.c14n.v1"
-}

changedInput schema / required

Previous value: -[
-  "offer_id",
-  "offer_revision",
-  "offer_revision_digest",
-  "input_schema_digest",
-  "output_schema_digest",
-  "canonicalizer_version",
-  "input",
-  "idempotency_key"
-]New value: +[
+  "offer_id",
+  "offer_revision",
+  "offer_revision_digest",
+  "input_schema_digest",
+  "output_schema_digest",
+  "input",
+  "idempotency_key"
+]

First observedSep 1, 2026

TDQS

A3.7/5.0

Behavior4/5

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

The description adds non-obvious behavioral context: results are 'immutable', failures are returned as a 'typed refusal', exactly one 'invocation envelope' is accepted, and payment material is never accepted from model-authored arguments. Annotations already signal idempotent and non-destructive behavior; the description complements them without contradiction, though side effects of preparation are not described.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two front-loaded sentences with no filler. The first sentence states the action, resource, and possible outcomes; the second adds a critical security constraint. Every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with 9 parameters, 7 required fields, nested objects, and no parameter coverage in the description, the high-level purpose and one security rule are insufficient. The agent is left to infer how offers, revisions, digests, and the invocation envelope relate, as well as when preparation would be required.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, and the description names none of the nine parameters such as offer_id, offer_revision, digests, idempotency_key, or parent_binding. The phrase 'invocation envelope' and the payment-material restriction give only minimal input semantics, leaving required parameters largely unexplained.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb ('Validate') and a specific resource ('one exact invocation envelope'), and states the outcome ('immutable preparation terms or a typed refusal'). This clearly differentiates the tool from siblings like get_invocation, cancel_invocation, and search_offers, even without naming them.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is implied by the word 'prepare' and the action of validating an invocation envelope, but there is no explicit when-to-use guidance or comparison to alternatives. The payment-material restriction is a useful when-not, but the description does not say when this tool should be chosen over related invocation tools.

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

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