lazaretto

known_bad_lookup

Read-onlyIdempotent

Check a SHA-256 against Lazaretto's known-bad indicator set (refreshed daily from abuse.ch). Free and anonymous. A miss only means this exact hash is not in the indicator set; it is not a clean verdict on the artifact.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`sha256`	Yes	64 hex chars, optionally sha256: prefixed

Output Schema

TableJSON Schema

Name	Required	Description
`known_bad`	Yes	matched is true on a hit, false on a miss. A miss is not a verdict on the artifact.
`disclaimer`	No
`target_hash`	Yes	The hash that was looked up, sha256: prefixed.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedAug 30, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "disclaimer": {
+      "type": "string"
+    },
+    "known_bad": {
+      "description": "matched is true on a hit, false on a miss. A miss is not a verdict on the artifact.",
+      "properties": {
+        "match_type": {
+          "type": "string"
+        },
+        "matched": {
+          "description": "null means the indicator set could not be consulted (fail closed), never treat null as clean.",
+          "type": [
+            "boolean",
+            "null"
+          ]
+        },
+        "note": {
+          "type": "string"
+        },
+        "sources": {
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        }
+      },
+      "required": [
+        "matched"
+      ],
+      "type": "object"
+    },
+    "target_hash": {
+      "description": "The hash that was looked up, sha256: prefixed.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "target_hash",
+    "known_bad"
+  ],
+  "type": "object"
+}

First observedJul 16, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, so the description does not need to repeat those. It adds valuable behavioral context by stating the indicator set is refreshed daily from abuse.ch and, crucially, that a miss is not a clean verdict on the artifact. This goes beyond the annotations by explaining interpretation semantics.

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?

The description is two sentences long, front-loads the core action and resource, and wastes no words. Every sentence adds value: the first establishes what the tool does, the second clarifies an important interpretation caveat. This is exemplary conciseness.

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

Completeness5/5

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

For a simple one-parameter lookup tool with a rich annotation set and an output schema (not shown but indicated), the description is complete. It covers the essential behavioral nuance (miss ≠ clean verdict) and the data freshness. Nothing an agent needs to correctly invoke the tool is missing.

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 parameter (sha256), which fully documents the format and optional prefix. The description adds no additional information about the parameter, but given the high coverage, a baseline of 3 is appropriate. No extra semantic value is provided beyond the schema.

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 clearly states the verb 'Check', the resource 'SHA-256 against Lazaretto's known-bad indicator set', and adds important context about being free and anonymous. It also clarifies the meaning of a miss. However, it does not explicitly differentiate from sibling tools like scan_artifact or check_lockfile, so it falls short of 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?

The description implies usage: you would use this to quickly check a hash against a known-bad list, and the 'free and anonymous' note hints at when this tool is appropriate. However, it does not explicitly state when to use this versus alternatives, nor does it mention any exclusions or prerequisites. The guidance is implicit rather than explicit.

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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