LicenseGuard
LicenseGuard is an MCP server that evaluates open-source dependency licenses against your distribution model and returns practical verdicts (allowed, review, blocked) with cited obligations.
Check a single dependency (
check_dependency_license): before adding or auditing one package, providing ecosystem, name, version, dependency scope, and how you ship the software.Scan entire manifests/lockfiles (
check_manifest_licenses): audit package-lock.json, pnpm-lock.yaml, yarn.lock, go.sum, Cargo.lock, poetry.lock, uv.lock, package.json, requirements.txt, go.mod, Cargo.toml and more, including transitive dependencies.Explain any license (
explain_license): get what a license requires across every shipping model at once, with optional linkage (dynamic/static/separate-process) for LGPL-family licenses.Choose a distribution model for each check: SaaS, distributed binary, on-prem delivery, internal-only, or library-published.
Use scope awareness for dependencies: runtime vs dev/build/test/optional, so build-time and dev dependencies that never ship are not treated as obligations.
Get actionable output: each check returns the license, verdict, obligations list, rationale, and a reference citation.
Works through the MCP protocol for coding agents and also exposes the same policy engine via a hosted HTTP endpoint and JSON API.
Checks npm package licenses against the project's distribution model, scanning package.json and package-lock.json files and resolving licenses from the npm registry.
Reviews .NET dependency licenses from packages.lock.json, .csproj, Directory.Packages.props, and packages.config, resolving license information from NuGet.
Audits Python dependency licenses using manifests such as requirements.txt, pyproject.toml, poetry.lock, and uv.lock, resolving package licenses from PyPI.
Scans Gemfile.lock and checks Ruby gem licenses against the selected distribution model using RubyGems registry data.
Click on "Install Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type
@followed by the MCP server name and your instructions, e.g., "@LicenseGuardCan I use AGPL-3.0 in our commercial SaaS?"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
LicenseGuard
A tool that determines whether the licenses of your OSS dependencies create legal obligations for your distribution model.
Production: https://license-guard.rcc-aoki.workers.dev
What's different
Existing license compliance products fall into two camps: "deep analysis but requires a sales call (FOSSA / Black Duck)" or "self-serve but shallow analysis (Snyk)"—and no product exists at the intersection.
The core differentiator is the analysis layer. The same license can lead to completely opposite conclusions depending on context.
Usage | AGPL-3.0 consequences |
Provided externally as a SaaS | Disclosure obligation applies |
Used only in internal systems | No obligation |
Delivered or distributed to customers | Disclosure obligation applies |
devDependency (not included in the deliverable) | No obligation |
The last row is decisive. Most existing tools don't distinguish between dev and runtime dependencies, so they raise warnings that cry wolf and get ignored.
Related MCP server: DepGuard
Using it from an agent
The need for this product arises not when you're searching the browser, but when you're adding a dependency. So the primary placement isn't search results—it's the agent's toolset.
claude mcp add licenseguard --transport http https://license-guard.rcc-aoki.workers.dev/mcpStateless Streamable HTTP, no authentication required. Tools provided:
Tool | Purpose |
| Call before adding a single dependency |
| Audit an entire manifest |
| Explain what a license requires across all distribution models |
The JSON API returns the same analysis.
curl "https://license-guard.rcc-aoki.workers.dev/api/pkg/pypi/pyload-ng?model=saas"
# => {"license":"AGPL-3.0-only","verdict":"blocked", ...}The agent-facing entry point is consolidated at /llms.txt.
Current phase
Phase 0 (validating willingness to pay) — MCP server and free web tool are published. Since the main battlefield is agent workflows rather than search, the validation metric isn't CTA click-through rate but MCP adoption and sustained call volume. The GitHub App (Phase 1) will be started after reviewing the validation results.
Supported ecosystems: npm / PyPI / Go modules / crates.io (Rust)
Format | Transitive dependencies | External lookup |
| Yes | Not needed (includes licenses) |
| Yes | Needed (amortized via shared cache) |
| Yes | Needed |
| Yes | Needed |
| ✗ direct dependencies only | Needed |
Passing a lock file lets you analyze transitive dependencies too (package-lock.json / pnpm-lock.yaml / yarn.lock).
Of these, package-lock.json includes license information, so no external lookup is needed at all. Lock files
include license information, so no external lookup is needed at all, and the exact versions actually installed
can be used as-is. Problematic licenses are more likely to sneak in as dependencies of dependencies than as directly added dependencies, so this is the real main event.
curl -X POST https://license-guard.rcc-aoki.workers.dev/api/scan -H 'content-type: application/json' -d "$(jq -Rs '{content: ., distributionModel: "saas"}' package-lock.json)"Development
npm install
npm test # 全テスト
npm run typecheck
npm run smoke # 実レジストリへの疎通確認
npm run e2e # 本番に対する E2E 6種
# ui Playwright で実ブラウザ
# a11y アクセシビリティ
# mcp 公式 MCP SDK クライアント
# load 並列実行時の一貫性
# adversarial 敵対的入力・境界値
# correctness 既知の正解との突き合わせ
# operational 経路間の一致・HTTP・キャッシュ
npm run dev # http://localhost:8787Even if all unit tests pass, some defects only surface when you run real data.
smoke and e2e run against production-equivalent external dependencies, so be sure to run them before every release.
Deployment:
npm run db:migrate
npm run deployDocumentation
Design spec: docs/specs/2026-08-19-license-guard-design.md
Phase 0 implementation plan: docs/superpowers/plans/2026-08-19-phase0-free-web-tool.md
Dependency OSS
Given the subject matter this product itself handles, all dependencies are limited to MIT / Apache-2.0 families. No disclosure obligation arises for our own SaaS.
Role | OSS | License |
SPDX expression parsing |
| MIT |
Web framework |
| MIT |
Go license data | ClearlyDefined API | Apache-2.0 |
Disclaimer
This tool presents information based on published license texts and dependency manifests—not legal advice. No attorney-client relationship is established by its use. The analysis is based on the license information declared in the manifest and does not cover all obligations or violations.
Available Tools
3 toolscheck_dependency_licenseCheck one dependency for license obligationsAInspect
Determine whether adding or keeping a single open source dependency creates a legal obligation, given how this project ships. Call this BEFORE adding a new dependency to a project, and when auditing an existing one. A permissive result means no source-disclosure duty; a blocked result means the license obligates you and the dependency should be replaced or the shipping model reconsidered.
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | Package name as written in the manifest, e.g. "express", "requests", "github.com/gin-gonic/gin", or "serde". | |
| scope | No | Where the dependency sits. Use "dev", "build", or "test" for anything that does not end up in the shipped artifact — those carry no distribution obligation. Defaults to "runtime". | |
| version | No | Exact version if known. Omit to use the latest published version, which may differ from what is installed. | |
| ecosystem | Yes | Package registry the dependency comes from. | |
| distribution_model | Yes | How the software incorporating this dependency reaches its users. This determines the answer: "saas" = users reach it over a network; "distributed-binary" = shipped as an app or binary; "on-prem-delivery" = installed in a customer environment; "internal-only" = never leaves your organization; "library-published" = released for others to depend on. |
Output Schema
| Name | Required | Description |
|---|---|---|
| license | Yes | |
| verdict | Yes | |
| rationale | Yes | |
| reference | No | |
| obligations | Yes |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden. It explains the meaning of results ('A permissive result means no source-disclosure duty; a blocked result means...') but does not state whether the operation is read-only, has side effects, or any error conditions. This is adequate but not rich; a note about being non-destructive would improve it.
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?
The description is two sentences, front-loaded with the core purpose, and immediately provides usage timing. Every sentence adds value: the first defines what it does and when to use it; the second explains result interpretation. No fluff or redundancy.
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?
Given 5 parameters (3 enums), an output schema, and no annotations, the description covers the key behavioral context: when to call, what question it answers, and how to interpret results. It ties the distribution_model to the shipping model. It does not mention error handling or edge cases, but the output schema likely handles that. Overall, it's complete for its complexity.
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 description coverage is 100%, so the schema already explains all parameters in detail (including enums and examples). The description adds no parameter-specific guidance beyond the schema, which meets the baseline for high coverage. It does hint at the importance of distribution_model by referencing 'how this project ships', but this is not about parameter syntax.
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?
The description clearly states the tool's purpose: 'Determine whether adding or keeping a single open source dependency creates a legal obligation.' It also contextualizes it with 'given how this project ships' and explicitly says to call it BEFORE adding a dependency, which distinguishes it from broader checks like check_manifest_licenses.
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?
It provides explicit guidance: 'Call this BEFORE adding a new dependency to a project, and when auditing an existing one.' It also explains what a permissive vs. blocked result means, giving actionable next steps. However, it does not mention when NOT to use this tool (e.g., for multiple dependencies) or name alternatives.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
check_manifest_licensesCheck a whole manifestAInspect
Scan an entire dependency manifest and report every dependency whose license creates an obligation for this shipping model. Use when reviewing a project as a whole, preparing for due diligence, or after a large dependency change. Pass a package-lock.json when one exists: problematic licenses usually arrive as transitive dependencies rather than ones you added directly, and only a lockfile reveals those.
| Name | Required | Description | Default |
|---|---|---|---|
| content | Yes | Full text of a lockfile or manifest. Accepted: package-lock.json, pnpm-lock.yaml, yarn.lock, go.sum, Cargo.lock, poetry.lock, uv.lock, package.json, requirements.txt, go.mod, Cargo.toml. The format is detected automatically. Prefer a lockfile: it covers transitive dependencies and carries exact versions. package-lock.json is best of all, since it embeds licenses and needs no registry lookups. | |
| distribution_model | Yes | How the software incorporating this dependency reaches its users. This determines the answer: "saas" = users reach it over a network; "distributed-binary" = shipped as an app or binary; "on-prem-delivery" = installed in a customer environment; "internal-only" = never leaves your organization; "library-published" = released for others to depend on. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses the tool's behavior (scans manifest, reports dependencies with obligations), notes automatic format detection, and explains that package-lock.json embeds licenses, avoiding registry lookups. It implies a read-only operation but does not explicitly state absence of side effects. Minor gap, but context is sufficient.
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?
The description is concise (three sentences) and front-loaded: the first sentence defines purpose, the second covers usage, and the third adds actionable input guidance. Every sentence earns its place with no fluff, and the structure flows logically.
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?
Given only two parameters, no output schema, and no annotations, the description fully covers the tool's purpose, when to use it, and how to provide input effectively. It also addresses the distinction from siblings, making it complete for the context. No gaps are evident.
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 baseline is 3. The description adds significant value by advising to pass a lockfile for transitive dependencies and explaining why package-lock.json is best (embeds licenses, no lookups). It also lists accepted formats implicitly through schema, but the description reinforces the preferred format and rationale, going beyond the schema.
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?
The description states a specific verb-resource pair: 'Scan an entire dependency manifest and report every dependency whose license creates an obligation for this shipping model.' It clearly distinguishes from sibling tools check_dependency_license (single dependency) and explain_license (license explanation) by focusing on a whole manifest and filtering based on the shipping model.
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?
Explicit usage context is given: 'Use when reviewing a project as a whole, preparing for due diligence, or after a large dependency change.' It also provides actionable advice to pass a lockfile (package-lock.json) and explains why it's preferred, covering when to use this tool over alternatives. This exceeds the requirement for clear context and exclusions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
explain_licenseExplain what a license requiresAInspect
Given an SPDX license identifier or expression, explain what it requires across every shipping model at once. Use when the question is about the license itself rather than a specific package — for example when comparing AGPL-3.0 against GPL-3.0 for a hosted service, or deciding what a project may safely depend on.
| Name | Required | Description | Default |
|---|---|---|---|
| license | Yes | SPDX identifier or expression, e.g. "AGPL-3.0-only", "Apache-2.0", or "(MIT OR GPL-2.0-only)". | |
| linkage | No | How the dependency is linked. Matters for LGPL-family licenses. Compiled languages such as Go and Rust normally link statically. Defaults to "dynamic". |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the transparency burden. It discloses that the tool covers all shipping models at once, which is a useful behavioral trait, but it does not describe return format, side effects, or assumptions about the linkage parameter. The description offers some insight but lacks a broader behavioral picture.
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 sentences, front-loaded with purpose and followed by usage context. No redundant words or filler. Every sentence adds value.
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?
Given no output schema, the description gives enough for an agent to know when and how to invoke the tool. It clearly differentiates from siblings and describes the input. It could briefly mention what the output entails (e.g., per-shipping-model breakdown), but the missing details are not critical for invoking correctly.
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 description coverage is 100%, so the schema already documents both parameters thoroughly. The tool description does not add extra meaning beyond the schema – it merely mentions the input in passing. Baseline of 3 applies because the schema does the heavy lifting.
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?
The description clearly states the action ('explain') and the resource (SPDX license identifier/expression), and specifies the scope ('what it requires across every shipping model at once'). It further distinguishes the tool from sibling tools by noting it is for the license itself 'rather than a specific package', with concrete examples.
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?
Explicitly provides a condition for use: 'Use when the question is about the license itself rather than a specific package'. Examples (comparing AGPL vs GPL, deciding what a project may depend on) clarify the intended scenario, and the phrasing implicitly contrasts with dependency-checking tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Tool Schema Changelog
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
3 tool updates
- First observed
check_dependency_license - First observed
check_manifest_licenses - First observed
explain_license
TDQS
Scored across 3 tools
Each tool has a clearly distinct purpose: explain_license focuses on understanding a license itself, check_dependency_license evaluates a single dependency in context, and check_manifest_licenses scans an entire manifest. There is no overlap or ambiguity between them.
All tool names follow a consistent verb_noun pattern (explain_license, check_dependency_license, check_manifest_licenses). The only minor deviation is that two tools start with 'check' while the third uses 'explain', but this is justified by the different action types.
With only 3 tools, the server is slightly on the lean side, but each tool covers a distinct and essential aspect of license management (understanding, single-dependency check, full-manifest scan). The count is appropriate for a focused utility server.
The tool surface covers the core workflows: understanding licenses, checking individual dependencies, and scanning entire manifests. A minor gap is the lack of a tool to handle bulk license explanations or compare multiple licenses directly, but the existing tools cover the primary use cases well.
Maintenance
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