x402-checks

Address Snapshot & Operator Policy Comparison

sanctions_address_screen

Read-onlyIdempotent

Screen an EVM wallet address or ISO country code by exact comparison against the identified sanctions address snapshot and existing operator block policy. Current legal status is unknown; is_sanctioned is null. valid=false preserves a local block; valid=null never authorizes a transaction. Names are not screened. Missing, stale or incomplete evidence is explicit; no UN/EU coverage or sanctions clearance is provided.

Input Schema

Name	Required	Description	Default
`subject`	Yes	EVM address (0x...) or ISO 3166-1 country code / jurisdiction name

Output Schema

Name	Required	Description	Default
`tool`	Yes
`scope`	No
`valid`	Yes
`reason`	No
`subject`	No
`match_type`	No
`is_sanctioned`	Yes
`blocklist_match`	Yes
`snapshot_sha256`	No
`snapshot_status`	No
`sanction_program`	No
`screening_status`	Yes
`current_legal_status`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

AddedOct 17, 2026
RemovedOct 15, 2026

Changed9 schema fields changedOct 13, 2026

addedOutput schema / properties / blocklist_match

Added value: +{
+  "type": [
+    "boolean",
+    "null"
+  ]
+}

addedOutput schema / properties / current_legal_status
```
Added value: +{
+  "type": "string"
+}
```
changedOutput schema / properties / is_sanctioned / type
```
Previous value: -"boolean"New value: +"null"
```

changedOutput schema / properties / sanction_program / type

Previous value: -"string"New value: +[
+  "string",
+  "null"
+]

addedOutput schema / properties / screening_status
```
Added value: +{
+  "type": "string"
+}
```
addedOutput schema / properties / snapshot_sha256
```
Added value: +{
+  "type": "string"
+}
```
addedOutput schema / properties / snapshot_status
```
Added value: +{
+  "type": "string"
+}
```

changedOutput schema / properties / valid / type

Previous value: -"boolean"New value: +[
+  "boolean",
+  "null"
+]

changedOutput schema / required

Previous value: -[
-  "tool",
-  "valid",
-  "is_sanctioned"
-]New value: +[
+  "tool",
+  "valid",
+  "is_sanctioned",
+  "blocklist_match",
+  "current_legal_status",
+  "screening_status"
+]

First observedOct 6, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations already declare a read-only, idempotent, open-world lookup, but the description adds context annotations cannot: matching is exact (not fuzzy), the snapshot may be stale, missing evidence is surfaced explicitly, and the null semantics never authorize a transaction. Some of this (is_sanctioned, valid) may duplicate the output schema, which slightly dilutes the added value.

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?

Four dense sentences, front-loaded with the screening action, and every sentence carries operational meaning (null semantics, exclusions, staleness). The telegraphic phrasing ('Current legal status is unknown; is_sanctioned is null') is compact at some cost to readability but wastes nothing.

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

Completeness4/5

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

With annotations covering safety and an output schema covering return fields, the remaining burden is scope and trust caveats, and the description addresses them thoroughly (exact match, snapshot staleness, no UN/EU coverage, no clearance). The only unaddressed item is how authoritative or dated the snapshot is.

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

Parameters3/5

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

Schema description coverage is 100% for the single subject parameter, so the baseline is 3. The description contributes the important constraint that the comparison is exact and that names are not accepted, which sharpens how an agent should format the input, but it adds no format details beyond the schema's own '0x...' / ISO 3166-1 guidance.

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?

States a specific verb (screen) and resource (EVM address or ISO country code) and pins the method precisely: exact comparison against a named sanctions snapshot plus operator block policy. This clearly separates it from the many format-validator siblings (iban_check, lei_check, e164_check) that share a similar input shape, though it never names those siblings directly.

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

Usage Guidelines4/5

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

Explicit scope exclusions do the routing work: 'Names are not screened' and 'no UN/EU coverage or sanctions clearance is provided' tell an agent when this tool is insufficient. It lacks an explicit 'use X instead' pointer to a sibling for name-based screening, so a small inference gap remains.

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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