Ausca

Admit or replay one Browser Session invocation

ausca_lease_browser

DestructiveIdempotent

Admit or replay one idempotent paid Browser Session invocation when settlement authority is supplied by the host boundary. Only envelopes for the browser.session offer are admitted on this resource.

Input Schema

Name	Required	Description	Default
`input`	Yes
`offer_id`	Yes
`offer_revision`	Yes
`idempotency_key`	Yes
`input_schema_digest`	Yes
`output_schema_digest`	Yes
`offer_revision_digest`	Yes

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed8 schema fields changedOct 25, 2026

removedOutput schema / $defs / ArtifactEvidence / properties / artifact_ref
```
Removed value: -{
-  "$ref": "#/$defs/ArtifactRef"
-}
```
addedOutput schema / $defs / ArtifactEvidence / properties / artifact_uri
```
Added value: +{
+  "$ref": "#/$defs/ArtifactUri"
+}
```

changedOutput schema / $defs / ArtifactEvidence / required

Previous value: -[
-  "artifact_ref",
-  "content_digest",
-  "media_type",
-  "size_bytes",
-  "created_at"
-]New value: +[
+  "artifact_uri",
+  "content_digest",
+  "media_type",
+  "size_bytes",
+  "created_at"
+]

removedOutput schema / $defs / ArtifactRef

Removed value: -{
-  "description": "Opaque artifact reference minted by artifact commitment. Relay it unchanged; its form is not part of the contract.",
-  "maxLength": 512,
-  "minLength": 1,
-  "type": "string"
-}

addedOutput schema / $defs / ArtifactUri

Added value: +{
+  "description": "Opaque artifact reference minted by artifact commitment. Relay it unchanged; its form is not part of the contract.",
+  "maxLength": 512,
+  "minLength": 1,
+  "type": "string"
+}

addedOutput schema / $defs / X402PaymentRequired / properties / accepts / items / title
```
Added value: +"X402PaymentRequirements"
```
addedOutput schema / $defs / X402PaymentRequired / properties / resource / title
```
Added value: +"X402ResourceInfo"
```
addedOutput schema / $defs / X402PaymentRequired / title
```
Added value: +"X402PaymentRequired"
```

Changed3 schema fields changedOct 16, 2026

removedInput schema / $defs / ParentBinding

Removed value: -{
-  "additionalProperties": false,
-  "properties": {
-    "execution_digest": {
-      "$ref": "#/$defs/Digest"
-    },
-    "invocation_id": {
-      "$ref": "#/$defs/Identifier"
-    }
-  },
-  "required": [
-    "invocation_id",
-    "execution_digest"
-  ],
-  "type": "object"
-}

removedInput schema / properties / attribution

Removed 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"
-}

removedInput schema / properties / parent_binding

Removed value: -{
-  "$ref": "#/$defs/ParentBinding"
-}

AddedSep 28, 2026

TDQS

B3.2/5.0

Behavior3/5

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

Annotations already declare idempotent, destructive, and open-world, so 'idempotent' in the text is redundant. The description does add real context: settlement authority comes from the host boundary and only browser.session envelopes are accepted. But it never explains what the destructiveHint actually entails (what state is destroyed), so a 3 fits given annotation coverage.

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

Conciseness4/5

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

Two tightly packed sentences with the action front-loaded and no filler. Dense domain jargon costs a bit of readability but nothing is wasted.

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

Completeness3/5

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

An output schema exists, so return values need not be described. But for a 7-parameter, destructive, settlement-dependent mutation with 0% schema coverage, the description does not explain the digest fields or idempotency semantics an agent needs to invoke correctly.

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% across all 7 required parameters, so the schema documents nothing. The description mentions idempotency and settlement authority in prose but maps none of the seven parameters (offer digests, idempotency_key, input) to their meaning, leaving the gap unaddressed.

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

Purpose4/5

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

The description states a specific verb pair (admit or replay) and names the resource (a Browser Session invocation), and it scopes admission to browser.session offer envelopes. It does not explicitly differentiate itself from siblings like ausca_prepare_invocation or ausca_get_invocation, keeping it from a 5.

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?

It gives a usage condition ('when settlement authority is supplied by the host boundary') and an admission constraint ('Only envelopes for the browser.session offer are admitted'). However, it never names an alternative tool or states when-not to use this one, leaving routing to inference.

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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