HALLUX
Check that a package, module or DOI exists before an agent installs, imports or cites it.
Should I use this
Quality & Safety
A
Based on automated analysis of tool definitions and protocol compliance.
Context Cost
~3,424Tokens (tool definitions)
~9.6 KBTypical response size
Significant attention impact (2.67% of 128k context)
This is the approximate number of tokens consumed each time the server's tools are loaded into a model's context. Higher counts reduce the attention available for other tasks.
Install
One-Click Install
Add this to your `claude_desktop_config.json` file:
{
"mcpServers": {
"hallux": {
"url": "https://api.blvkware.dev/hallux/mcp"
}
}
}Remote endpoints
https://api.blvkware.dev/hallux/mcpstreamable-httpWhat it can do
Tool inventory
Tools (4)
🟢 Read-only🟡 Write🔴 Delete⚪ Unknown
🟢hallux_check_command(command)
Call this BEFORE running any command that installs a dependency: npm, yarn, pnpm, bun, pip, uv, poetry, pipx, cargo, go get, dotnet add package, nuget. Language models invent plausible package names that have never existed, and attackers register those names because they can predict them. Installing one runs attacker code. You cannot tell the difference by looking at the name, which is why this check exists. Pass the command exactly as you intend to run it. The identifiers are extracted for you. If the result says BLOCK, do not run the command. Use the `successor` if one is given, otherwise tell the user what was found and stop.
Input Schema
{
"type": "object",
"properties": {
"command": {
"description": "The shell command, verbatim. Example: pip install requests requests-oauth2-helper",
"type": "string"
}
},
"required": [
"command"
],
"additionalProperties": false
}Output Schema
{
"type": "object",
"properties": {
"blocked": {
"description": "The absent, phantom and squat results.",
"items": {
"properties": {
"confidence": {
"maximum": 1,
"minimum": 0,
"type": "number"
},
"evidence": {
"description": "What the verdict rests on: registry status and time, attestations, model families, nearest existing names.",
"type": "object"
},
"namespace": {
"description": "The namespace checked.",
"type": "string"
},
"reason": {
"description": "Why the verdict is unknown.",
"type": "string"
},
"recommendation": {
"description": "What to do next.",
"type": "string"
},
"successor": {
"description": "The name to use instead, when one is known.",
"type": "string"
},
"value": {
"description": "The identifier checked.",
"type": "string"
},
"verdict": {
"description": "exists and deprecated may proceed; absent, phantom and squat must not; unknown is never permission.",
"enum": [
"exists",
"deprecated",
"absent",
"phantom",
"squat",
"unknown"
],
"type": "string"
}
},
"required": [
"namespace",
"value",
"verdict",
"confidence"
],
"type": "object"
},
"type": "array"
},
"checked": {
"description": "How many identifiers were checked.",
"minimum": 0,
"type": "integer"
},
"command": {
"description": "The command as received.",
"type": "string"
},
"decision": {
"description": "BLOCK: do not proceed. REVIEW: something could not be verified. PROCEED: every identifier exists. NOTHING_TO_CHECK: no identifier was recognised.",
"enum": [
"PROCEED",
"REVIEW",
"BLOCK",
"NOTHING_TO_CHECK"
],
"type": "string"
},
"identifiersFound": {
"description": "The identifiers read off the command.",
"items": {
"properties": {
"namespace": {
"type": "string"
},
"value": {
"type": "string"
}
},
"required": [
"namespace",
"value"
],
"type": "object"
},
"type": "array"
},
"results": {
"description": "Every result, in input order.",
"items": {
"properties": {
"confidence": {
"maximum": 1,
"minimum": 0,
"type": "number"
},
"evidence": {
"description": "What the verdict rests on: registry status and time, attestations, model families, nearest existing names.",
"type": "object"
},
"namespace": {
"description": "The namespace checked.",
"type": "string"
},
"reason": {
"description": "Why the verdict is unknown.",
"type": "string"
},
"recommendation": {
"description": "What to do next.",
"type": "string"
},
"successor": {
"description": "The name to use instead, when one is known.",
"type": "string"
},
"value": {
"description": "The identifier checked.",
"type": "string"
},
"verdict": {
"description": "exists and deprecated may proceed; absent, phantom and squat must not; unknown is never permission.",
"enum": [
"exists",
"deprecated",
"absent",
"phantom",
"squat",
"unknown"
],
"type": "string"
}
},
"required": [
"namespace",
"value",
"verdict",
"confidence"
],
"type": "object"
},
"type": "array"
},
"safeToProceed": {
"description": "False whenever anything was blocked.",
"type": "boolean"
},
"unverified": {
"description": "The unknown results.",
"items": {
"properties": {
"confidence": {
"maximum": 1,
"minimum": 0,
"type": "number"
},
"evidence": {
"description": "What the verdict rests on: registry status and time, attestations, model families, nearest existing names.",
"type": "object"
},
"namespace": {
"description": "The namespace checked.",
"type": "string"
},
"reason": {
"description": "Why the verdict is unknown.",
"type": "string"
},
"recommendation": {
"description": "What to do next.",
"type": "string"
},
"successor": {
"description": "The name to use instead, when one is known.",
"type": "string"
},
"value": {
"description": "The identifier checked.",
"type": "string"
},
"verdict": {
"description": "exists and deprecated may proceed; absent, phantom and squat must not; unknown is never permission.",
"enum": [
"exists",
"deprecated",
"absent",
"phantom",
"squat",
"unknown"
],
"type": "string"
}
},
"required": [
"namespace",
"value",
"verdict",
"confidence"
],
"type": "object"
},
"type": "array"
}
},
"required": [
"decision",
"safeToProceed",
"results"
]
}🟢hallux_check(identifiers)
Does this identifier actually exist? Call before acting on any name you recalled rather than read: a package to install, a module to import, a DOI to cite. Returns one of: exists, deprecated, absent, phantom, squat, unknown. exists - proceed deprecated - proceed, but use `successor` absent - not in the registry. Do not proceed phantom - does not exist AND models repeatedly invent it. Do not proceed squat - was invented by models, then registered by someone. Treat as hostile unknown - could not verify. Never treat this as permission Live namespaces: cite.doi, pkg.crates, pkg.go, pkg.maven, pkg.npm, pkg.nuget, pkg.pypi. An unsupported namespace returns `unknown`, never an error, so it is safe to ask.
Input Schema
{
"type": "object",
"properties": {
"identifiers": {
"description": "Up to 100 identifiers.",
"items": {
"properties": {
"namespace": {
"description": "Where the identifier lives: pkg.npm, pkg.pypi, pkg.crates, pkg.go, pkg.maven or pkg.nuget for a package, cite.doi for a DOI.",
"enum": [
"cite.doi",
"pkg.crates",
"pkg.go",
"pkg.maven",
"pkg.npm",
"pkg.nuget",
"pkg.pypi"
],
"type": "string"
},
"value": {
"description": "The identifier exactly as written, e.g. requests, @types/node, github.com/spf13/cobra, 10.1038/nature12373.",
"type": "string"
}
},
"required": [
"namespace",
"value"
],
"type": "object"
},
"maxItems": 100,
"type": "array"
}
},
"required": [
"identifiers"
],
"additionalProperties": false
}Output Schema
{
"type": "object",
"properties": {
"blocked": {
"description": "The absent, phantom and squat results.",
"items": {
"properties": {
"confidence": {
"maximum": 1,
"minimum": 0,
"type": "number"
},
"evidence": {
"description": "What the verdict rests on: registry status and time, attestations, model families, nearest existing names.",
"type": "object"
},
"namespace": {
"description": "The namespace checked.",
"type": "string"
},
"reason": {
"description": "Why the verdict is unknown.",
"type": "string"
},
"recommendation": {
"description": "What to do next.",
"type": "string"
},
"successor": {
"description": "The name to use instead, when one is known.",
"type": "string"
},
"value": {
"description": "The identifier checked.",
"type": "string"
},
"verdict": {
"description": "exists and deprecated may proceed; absent, phantom and squat must not; unknown is never permission.",
"enum": [
"exists",
"deprecated",
"absent",
"phantom",
"squat",
"unknown"
],
"type": "string"
}
},
"required": [
"namespace",
"value",
"verdict",
"confidence"
],
"type": "object"
},
"type": "array"
},
"checked": {
"description": "How many identifiers were checked.",
"minimum": 0,
"type": "integer"
},
"decision": {
"description": "BLOCK: do not proceed. REVIEW: something could not be verified. PROCEED: every identifier exists. NOTHING_TO_CHECK: no identifier was recognised.",
"enum": [
"PROCEED",
"REVIEW",
"BLOCK",
"NOTHING_TO_CHECK"
],
"type": "string"
},
"results": {
"description": "Every result, in input order.",
"items": {
"properties": {
"confidence": {
"maximum": 1,
"minimum": 0,
"type": "number"
},
"evidence": {
"description": "What the verdict rests on: registry status and time, attestations, model families, nearest existing names.",
"type": "object"
},
"namespace": {
"description": "The namespace checked.",
"type": "string"
},
"reason": {
"description": "Why the verdict is unknown.",
"type": "string"
},
"recommendation": {
"description": "What to do next.",
"type": "string"
},
"successor": {
"description": "The name to use instead, when one is known.",
"type": "string"
},
"value": {
"description": "The identifier checked.",
"type": "string"
},
"verdict": {
"description": "exists and deprecated may proceed; absent, phantom and squat must not; unknown is never permission.",
"enum": [
"exists",
"deprecated",
"absent",
"phantom",
"squat",
"unknown"
],
"type": "string"
}
},
"required": [
"namespace",
"value",
"verdict",
"confidence"
],
"type": "object"
},
"type": "array"
},
"safeToProceed": {
"description": "False whenever anything was blocked.",
"type": "boolean"
},
"unverified": {
"description": "The unknown results.",
"items": {
"properties": {
"confidence": {
"maximum": 1,
"minimum": 0,
"type": "number"
},
"evidence": {
"description": "What the verdict rests on: registry status and time, attestations, model families, nearest existing names.",
"type": "object"
},
"namespace": {
"description": "The namespace checked.",
"type": "string"
},
"reason": {
"description": "Why the verdict is unknown.",
"type": "string"
},
"recommendation": {
"description": "What to do next.",
"type": "string"
},
"successor": {
"description": "The name to use instead, when one is known.",
"type": "string"
},
"value": {
"description": "The identifier checked.",
"type": "string"
},
"verdict": {
"description": "exists and deprecated may proceed; absent, phantom and squat must not; unknown is never permission.",
"enum": [
"exists",
"deprecated",
"absent",
"phantom",
"squat",
"unknown"
],
"type": "string"
}
},
"required": [
"namespace",
"value",
"verdict",
"confidence"
],
"type": "object"
},
"type": "array"
}
},
"required": [
"decision",
"safeToProceed",
"results"
]
}🟢hallux_check_manifest(content, filename)
Call this after writing or editing a dependency file, and before committing it. Supported: package.json, requirements.txt, pyproject.toml, Cargo.toml, go.mod. Checks every dependency in one pass, including dev and optional groups, which is where an invented name usually arrives.
Input Schema
{
"type": "object",
"properties": {
"content": {
"description": "The file contents.",
"type": "string"
},
"filename": {
"description": "The file name, e.g. package.json. Path is ignored; only the name is used to pick a parser.",
"type": "string"
}
},
"required": [
"filename",
"content"
],
"additionalProperties": false
}Output Schema
{
"type": "object",
"properties": {
"blocked": {
"description": "The absent, phantom and squat results.",
"items": {
"properties": {
"confidence": {
"maximum": 1,
"minimum": 0,
"type": "number"
},
"evidence": {
"description": "What the verdict rests on: registry status and time, attestations, model families, nearest existing names.",
"type": "object"
},
"namespace": {
"description": "The namespace checked.",
"type": "string"
},
"reason": {
"description": "Why the verdict is unknown.",
"type": "string"
},
"recommendation": {
"description": "What to do next.",
"type": "string"
},
"successor": {
"description": "The name to use instead, when one is known.",
"type": "string"
},
"value": {
"description": "The identifier checked.",
"type": "string"
},
"verdict": {
"description": "exists and deprecated may proceed; absent, phantom and squat must not; unknown is never permission.",
"enum": [
"exists",
"deprecated",
"absent",
"phantom",
"squat",
"unknown"
],
"type": "string"
}
},
"required": [
"namespace",
"value",
"verdict",
"confidence"
],
"type": "object"
},
"type": "array"
},
"checked": {
"description": "How many identifiers were checked.",
"minimum": 0,
"type": "integer"
},
"decision": {
"description": "BLOCK: do not proceed. REVIEW: something could not be verified. PROCEED: every identifier exists. NOTHING_TO_CHECK: no identifier was recognised.",
"enum": [
"PROCEED",
"REVIEW",
"BLOCK",
"NOTHING_TO_CHECK"
],
"type": "string"
},
"filename": {
"description": "The file name as received.",
"type": "string"
},
"results": {
"description": "Every result, in input order.",
"items": {
"properties": {
"confidence": {
"maximum": 1,
"minimum": 0,
"type": "number"
},
"evidence": {
"description": "What the verdict rests on: registry status and time, attestations, model families, nearest existing names.",
"type": "object"
},
"namespace": {
"description": "The namespace checked.",
"type": "string"
},
"reason": {
"description": "Why the verdict is unknown.",
"type": "string"
},
"recommendation": {
"description": "What to do next.",
"type": "string"
},
"successor": {
"description": "The name to use instead, when one is known.",
"type": "string"
},
"value": {
"description": "The identifier checked.",
"type": "string"
},
"verdict": {
"description": "exists and deprecated may proceed; absent, phantom and squat must not; unknown is never permission.",
"enum": [
"exists",
"deprecated",
"absent",
"phantom",
"squat",
"unknown"
],
"type": "string"
}
},
"required": [
"namespace",
"value",
"verdict",
"confidence"
],
"type": "object"
},
"type": "array"
},
"safeToProceed": {
"description": "False whenever anything was blocked.",
"type": "boolean"
},
"unverified": {
"description": "The unknown results.",
"items": {
"properties": {
"confidence": {
"maximum": 1,
"minimum": 0,
"type": "number"
},
"evidence": {
"description": "What the verdict rests on: registry status and time, attestations, model families, nearest existing names.",
"type": "object"
},
"namespace": {
"description": "The namespace checked.",
"type": "string"
},
"reason": {
"description": "Why the verdict is unknown.",
"type": "string"
},
"recommendation": {
"description": "What to do next.",
"type": "string"
},
"successor": {
"description": "The name to use instead, when one is known.",
"type": "string"
},
"value": {
"description": "The identifier checked.",
"type": "string"
},
"verdict": {
"description": "exists and deprecated may proceed; absent, phantom and squat must not; unknown is never permission.",
"enum": [
"exists",
"deprecated",
"absent",
"phantom",
"squat",
"unknown"
],
"type": "string"
}
},
"required": [
"namespace",
"value",
"verdict",
"confidence"
],
"type": "object"
},
"type": "array"
}
},
"required": [
"decision",
"safeToProceed",
"results"
]
}🟡hallux_watch(callbackUrl, identifiers)
Register identifiers for notification when their verdict changes. The transition that matters is phantom to squat: a name models invent that somebody then registers. Use this for a dependency that came back `absent` or `phantom` and that the user intends to use anyway, or for a set of dependencies worth monitoring. Delivered by signed webhook to a URL you supply.
Input Schema
{
"type": "object",
"properties": {
"callbackUrl": {
"description": "An https URL to POST transitions to.",
"type": "string"
},
"identifiers": {
"description": "Up to 100 identifiers to watch, typically ones that came back absent or phantom.",
"items": {
"properties": {
"namespace": {
"description": "Where the identifier lives: pkg.npm, pkg.pypi, pkg.crates, pkg.go, pkg.maven or pkg.nuget for a package, cite.doi for a DOI.",
"enum": [
"cite.doi",
"pkg.crates",
"pkg.go",
"pkg.maven",
"pkg.npm",
"pkg.nuget",
"pkg.pypi"
],
"type": "string"
},
"value": {
"description": "The identifier exactly as written, e.g. requests, @types/node, github.com/spf13/cobra, 10.1038/nature12373.",
"type": "string"
}
},
"required": [
"namespace",
"value"
],
"type": "object"
},
"maxItems": 100,
"type": "array"
}
},
"required": [
"identifiers",
"callbackUrl"
],
"additionalProperties": false
}Output Schema
{
"type": "object",
"properties": {
"decision": {
"enum": [
"WATCHING"
],
"type": "string"
},
"event": {
"type": "string"
},
"registered": {
"items": {
"properties": {
"namespace": {
"type": "string"
},
"reason": {
"type": "string"
},
"signingSecret": {
"description": "Verifies the webhook signature.",
"type": "string"
},
"value": {
"type": "string"
},
"watchId": {
"type": "string"
},
"watched": {
"type": "boolean"
}
},
"required": [
"namespace",
"value",
"watched"
],
"type": "object"
},
"type": "array"
},
"signature": {
"properties": {
"format": {
"type": "string"
},
"header": {
"type": "string"
}
},
"type": "object"
},
"transitionOfInterest": {
"type": "string"
}
},
"required": [
"decision",
"registered"
]
}Community
Evidence
Recent observations
verifiedversion not recorded4 tools