Look up URLhaus metadata for an MD5 or SHA-256 malware-payload hash and return a bounded set of associated URLs. This tool does not download the payload.
| Name | Required | Description | Default |
|---|---|---|---|
| hash | Yes | Exactly 32 hexadecimal MD5 characters or 64 hexadecimal SHA-256 characters. | |
| limit | No | Maximum records to return (default 20, max 50). |
Changes observed during successful MCP inspections.
Input schema / properties / limit / maximumAdded value: +50Input schema / properties / limit / minimumAdded value: +1Input schema / properties / limit / typePrevious value: -"number"New value: +"integer"Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover readOnly, idempotent, non-destructive and openWorld, so the bar is lower. The description adds real value by noting the result set is bounded and, notably, that the tool does not download the payload - a meaningful boundary for a threat-intel lookup.
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 tight sentences, zero waste. The core purpose is front-loaded, and the disambiguating non-download caveat is placed second where it belongs.
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?
No output schema exists, but the description gives the return shape at a high level ('bounded set of associated URLs') and annotations carry the safety profile, so an agent has enough to call it correctly. Only minor gaps remain (pagination/empty-result behavior).
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?
Schema coverage is 100%, so hash format and the limit default/max are fully documented in the schema. The description restates the hash types but adds no syntax or semantics beyond the schema, making 3 the correct baseline.
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 (look up) and resource (URLhaus metadata) tied to a precise input type (MD5/SHA-256 malware-payload hash), which differentiates it from lookup_host/lookup_url siblings. It stops short of explicitly naming alternatives, but the hash-keyed scope is unambiguous.
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?
Usage is implied by the input type: this tool is for when you have a payload hash. However, it never states when to prefer it over sibling tools like urlhaus_lookup_signature or urlhaus_recent_payloads, or any exclusions. Guidance is inferable but not stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.