Foundry
Home Schema

Nextflow parameter schema (nf-schema meta-schema)

JSON Schema (Draft 2020-12) meta-schema validating per-pipeline nextflow_schema.json files. Upstream from nextflow-io/nf-schema.

draft schemasource/nextflow
Revised
2026-05-05
Rev
1
Molds
Related
schema nextflow-parameters-meta @galaxy-foundry/summarize-nextflow upstream ↗
No schema registered for nextflow-parameters-meta. Add an entry to site/src/lib/schema-registry.ts.

JSON Schema (Draft 2020-12) vendored verbatim from nextflow-io/nf-schema at SHA bde406e. Validates every pipeline’s nextflow_schema.json — the parameter-surface contract consumed by the runtime nf-schema plugin, the nf-co.re schema builder, nf-core launch, and Seqera Platform.

Operational role. This is the meta-schema referenced by summarize-nextflow §3: “When nextflow_schema.json exists (nf-core), prefer it as the source of truth for type, description, and required — it is real JSON Schema, copy verbatim.” This schema pins exactly which JSON Schema subset and which nf-core extensions are legal, so the cast skill emitting summary-nextflow.schema.json’s params[] block can validate its source rather than guess.

Draft-version note. This is the only Foundry-vendored schema currently authored against JSON Schema Draft 2020-12 (others are Draft-07). Validators consuming this schema must be Draft-2020-12-capable; AJV needs import Ajv from "ajv/dist/2020.js" rather than the default Draft-07 import. The Foundry’s own validator (scripts/validate.ts) only validates Foundry frontmatter (Draft-07) and does not load this schema as a meta — there’s no impedance.

Source-of-truth chain:

  1. parameters_meta_schema.json in nextflow-io/nf-schema.
  2. Vendored verbatim into content/schemas/nextflow-parameters-meta.schema.json, pinned at upstream’s SHA.
  3. Re-sync: curl -sL https://raw.githubusercontent.com/nextflow-io/nf-schema/<sha>/parameters_meta_schema.json -o content/schemas/nextflow-parameters-meta.schema.json and bump the SHA.

Top-level shape

A valid nextflow_schema.json is an object with required keys $schema, $id, title, description, type (constrained to object). Optional: $defs (parameter groups, the canonical nf-core idiom), allOf (composes the groups).

Each parameter property must declare type ∈ [string, boolean, integer, number] — narrower than vanilla JSON Schema; arrays and objects are deliberately disallowed at the top level (the samplesheetToList plugin handles tabular data outside the parameter schema). Optional keywords:

  • format ∈ [file-path, directory-path, path, file-path-pattern] — semantic enrichment for path-shaped params.
  • exists (boolean) — runtime existence check.
  • mimetype (.+/.+) — sniffed at validation time.
  • pattern, schema — string constraints; schema references a sample-sheet sub-schema.
  • description, help_text, errorMessage, fa_icon (^fa…), hidden.
  • minLength, maxLength, minimum, maximum — integers.

Parameter groups under $defs themselves require title, type (object), properties. Optional description, fa_icon, required — the same enrichment vocabulary.

Upstream license

Apache-2.0. See LICENSES/nf-schema.LICENSE.

Incoming References (1)