N8n:public API Skill for Cursor

Public API v1

Public API v1 lives in packages/cli/src/public-api/v1/, mounted at /api/v1

with API-key auth and public error formatting via PublicApiControllerRegistry

(packages/cli/src/public-api/public-api-controller.registry.ts).

Two rule tiers: invariants (never break) and team defaults (follow unless

an existing public contract forces otherwise). When this skill and the code

disagree on a detail, the code wins — so open the files below. That is a reason to

check the code, not license to drop a team default.

Non-negotiable rules

• New endpoints are @PublicApiController classes under v1/controllers/, one

*.public.controller.ts per feature. A controller is a class — never

export = (the legacy tuple style; require-public-api-controller flags it).

• Public API and internal REST are separate HTTP surfaces. A public controller

never calls an internal controller/endpoint; both reuse the same service.

• Controllers and handlers delegate to a service — never import a repository or

Container.get(…Repository) (no-repository-in-public-api-handler).

• Input/output go through DTOs from @n8n/api-types; every JSON route declares

@ApiResponse(Dto).

• Register each controller via a side-effect import in v1/controllers/index.ts

(public-api-controllers.test.ts fails otherwise).

• Don't add business logic to legacy express-openapi-validator (EOV) handlers.
• Migrating a legacy endpoint must not change its public contract.

These are n8n-local-rules ESLint rules (see packages/cli/eslint.config.mjs)

and can't be silenced inline (no-public-api-guardrail-disable). The off

allowlist there covers pre-existing legacy files only — it's shrink-only, don't

add to it.

Team defaults

• List endpoints: cursor-based pagination (internal API uses both cursor- and

page-based — don't copy an internal endpoint's model).

• Updates: full-object PUT, not PATCH. A successful GET body should be

acceptable as a PUT body for the same resource (round-trip), aside from

server-managed/immutable fields.

• Strict input DTOs; output DTOs are an allowlist of public fields.
• Never return real secrets/tokens in responses or error details — mask with the

resource's sentinel/placeholder (or omit). Echoing that sentinel on PUT

means keep; any other value replaces. Detail:

Updates and write-only secrets.

• "Test connection/config" endpoints validate the request body (test-before-save).

Architecture

Public and internal are sibling routes over one shared, HTTP-agnostic service;

neither calls the other.

GET /rest/tags    → TagsController         ┐  JWT auth, internal shape
                                            ├─→ TagService
GET /api/v1/tags  → TagsPublicController   ┘  API-key auth, public DTO

Reuse the service behavior. Reuse a DTO only when public and internal contracts

are intentionally identical; otherwise make a public-specific DTO that doesn't

depend on a UI-oriented internal shape.

Before editing

Open these — they are the source of truth, not this skill:

• v1/controllers/ — copy structure from tags.public.controller.ts (list +

cursor) or workflows.public.controller.ts (@Param + @ProjectScope), and

index.ts for the barrel.

• Decorators in packages/@n8n/decorators/src/controller/:

public-api-controller.ts, api-key-scope.ts, api-response.ts,

api-error-response.ts, api-summary.ts, api-description.ts, api-tags.ts,

route.ts, scoped.ts, args.ts, licensed.ts.

• The OpenAPI generator (reads the decorators above, no hand-written YAML

needed for a controller route): v1/openapi-gen/generate.ts,

v1/openapi-gen/decorator-routes.ts.

• Pagination helpers: v1/shared/services/pagination.service.ts

(decodeCursor, encodeNextCursor).

• DTOs: packages/@n8n/api-types/src/dto/.
• Gating tests: v1/__tests__/public-api-controllers.test.ts,

v1/__tests__/scope-parity.test.ts,

v1/openapi-gen/__tests__/generated-spec-drift.test.ts.

• The internal controller for this resource and its neighboring functional tests.

Declaring a controller

A controller is a class marked @PublicApiController('/base') that injects the

shared service via its constructor and delegates to it. Copy the shape from an

existing controller in v1/controllers/ with the same operation type and auth

model; reuse only what applies. Decorators, all from @n8n/decorators:

| Decorator | Use |

|---|---|

| @PublicApiController('/base') | Class marker; mounts routes at /api/v1/base. |

| @Get/@Post/@Put/@Patch/@Delete('/path') | Route method. |

| @ApiKeyScope('res:action') | API-key grant check. |

| @ProjectScope/@GlobalScope('res:action') | User RBAC check. |

| @ApiResponse(status) / @ApiResponse(status, Dto) | Success status + (optional) output DTO; registry .parse()s + strips the return value. Exactly one per route — a second @ApiResponse throws. 204 can't carry a DTO — throws. |

| @ApiErrorResponse(status) | Declares an additional documented non-2xx status (e.g. 404, 409). Stack multiple for more than one. 400/401/403 are added automatically (body/query present, always, and @ApiKeyScope present, respectively) — don't declare those yourself. |

| @ApiSummary(text) / @ApiDescription(text) / @ApiTags([...]) | OpenAPI summary/description/tags. @ApiTags sorts alphabetically regardless of the order you pass. All optional but expected on every real route. |

| @Query / @Body / @Param('name') | Bind + validate via a Z.class DTO / path param. |

| @Licensed('feat') | Not yet enforced for @PublicApiController routes — PublicApiControllerRegistry doesn't read licenseFeature (only the internal @RestController registry does). If the endpoint gates an EE feature, check the license manually in the handler (Container.get(License).isLicensed(LICENSE_FEATURES.X), throwing ForbiddenError on failure) instead of relying on this decorator alone. |

Authorization (easy to get wrong)

• @ApiKeyScope (what the API key is granted) and @ProjectScope/@GlobalScope

(what the user may do) are independent. Use both when the model needs both.

• @ProjectScope reads req.params as-is and does not remap id — name the path

param what the resolver expects (workflowId, credentialId, projectId,

dataTableId, …). A generic id often fails.

• @ApiKeyScope takes a string, { anyOf: [...] }, or { allOf: [...] } — never

a bare array. The scope must exist in the permissions registry

(API_KEY_RESOURCES in @n8n/permissions); scope-parity.test.ts fails on an

orphan scope.

DTOs

• Build the public response shape explicitly; don't return an ORM entity and lean

on @ApiResponse stripping to hide fields.

• Treat the output DTO as an allowlist. Re-check nested relations, ownership

fields, tokens, and encrypted values.

• Make input DTOs strict so unknown/partial fields aren't silently accepted.
• Secrets: never return a real secret; use the resource's sentinel/placeholder

(or omit). See Updates and write-only secrets.

List endpoints (cursor pagination)

Copy the cursor flow from tags.public.controller.ts. Use publicApiPaginationSchema

plus decodeCursor / encodeNextCursor from the shared pagination service; the

cursor is opaque; return { data, nextCursor } (never a bare array) with

nextCursor: null on the last page; an invalid cursor is a 400. Preserve an

existing endpoint's pagination as-is. Detail:

List endpoints and cursor pagination.

Wiring checklist

• v1/controllers/<feature>.public.controller.ts + side-effect import in

v1/controllers/index.ts.

• Public DTO in @n8n/api-types + export from the barrel (src/dto/).
• @ApiKeyScope value exists in the permissions registry.
• Don't hand-write the OpenAPI path or x-required-scope for a controller

route — the generator (v1/openapi-gen/generate.ts) builds it from your

decorators (@ApiSummary/@ApiDescription/@ApiTags/@ApiKeyScope/

@ApiResponse/@ApiErrorResponse). Run the full pnpm build and commit

the regenerated handlers/<feature>/spec/paths/*.generated.yml fragment(s)

and openapi.decorator-routes.generated.yml —

generated-spec-drift.test.ts fails CI if they're stale. `pnpm run

build:data` alone is not enough after touching a controller: it runs

the generator against the already-compiled dist/, so a new/changed

controller silently doesn't show up unless tsc ran first.

• Add the route to packages/nodes-base/nodes/N8n/n8n-api-coverage.json.
• Tests.

Testing

Always cover: happy path, input-validation failure, missing API-key scope, RBAC

denial. Prefer covering the business path in

packages/cli/test/integration/public-api/ (real HTTP + DB); mocked-service unit

tests don't replace that. Add the cases that apply (cursor pages,

not-found/conflict, no sensitive fields, credential keep/replace, migration

contract) — see Testing matrix. Match the nearest

existing tests.

More detail (reference.md)

• List endpoints and cursor pagination
• Updates and write-only secrets
• Test-before-save endpoints
• Errors
• Testing matrix
• Migrating legacy EOV endpoints