Convert between YAML 1.2 and JSON using the high-performance ref struct tokenizer.

Apache-2.0Auto-check passedTesting & QA

Install Corvus YAML

skills CLI
$ npx skills add corvus-dotnet/Corvus.JsonSchema --skill corvus-yaml -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install corvus-dotnet/Corvus.JsonSchema corvus-yaml --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/corvus-dotnet/Corvus.JsonSchema.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.github/skills/corvus-yaml .claude/skills/corvus-yaml && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
corvus-yaml
GitHub stars
199
Token cost
~1.2k tokens
SKILL.md length
337 words
Files
1
Skills in repo
26
Repo updated
First seen
Licence
Apache-2.0

At a glance

Convert between YAML 1.2 and JSON using the high-performance ref struct tokenizer.

  • : YAML-to-JSON conversion
  • SKILL.md covers Overview, Two Packages, Basic Usage and Schema Modes, plus 5 more sections
  • Calls dotnet
  • JSON-to-YAML conversion

What it does

Corvus YAML is an agent skill from corvus-dotnet/Corvus.JsonSchema. Convert between YAML 1.2 and JSON using the high-performance ref struct tokenizer. Covers the two packages (Corvus.Text.Json.Yaml for full integration, Corvus.Yaml.SystemTextJson for System.Text.Json-only), YAML→JSON and JSON→YAML conversion, schema modes, anchor/alias support, multi-document streams, Utf8YamlWriter, and 100% yaml-test-suite JSON-testable conformance (373 of 402 tests). USE FOR: YAML-to-JSON conversion, JSON-to-YAML conversion, understanding the tokenizer architecture, troubleshooting YAML…

Its SKILL.md is about 1.2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Testing & QA, covering Test generation. The repository describes itself as: Support for Json Schema validation and entity generation. The licence is Apache-2.0.

When your agent uses it

  • : YAML-to-JSON conversion
  • JSON-to-YAML conversion
  • Understanding the tokenizer architecture
  • Troubleshooting YAML parsing issues

Example prompts

  • “/corvus-yaml”

What it can do on your machine

Read from SKILL.md and the folder at commit b9e3040. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • dotnet

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Corvus YAML loads about 1.2k tokens when it runs. Until then it costs about 150 tokens; SKILL.md has 337 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~150
When it runs · the whole SKILL.md, loaded when a task matches
~1.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from corvus-dotnet/Corvus.JsonSchema at commit b9e3040, republished under its Apache-2.0 licence (© corvus-dotnet). 337 words, ~1,172 tokens.

Download SKILL.mdSave it as .claude/skills/corvus-yaml/SKILL.md (or your agent's skills folder).
name
corvus-yaml
description
Convert between YAML 1.2 and JSON using the high-performance ref struct tokenizer. Covers the two packages (Corvus.Text.Json.Yaml for full integration, Corvus.Yaml.SystemTextJson for System.Text.Json-only), YAML→JSON and JSON→YAML conversion, schema modes, anchor/alias support, multi-document streams, Utf8YamlWriter, and 100% yaml-test-suite JSON-testable conformance (373 of 402 tests). USE FOR: YAML-to-JSON conversion, JSON-to-YAML conversion, understanding the tokenizer architecture, troubleshooting YAML parsing issues. DO NOT USE FOR: JSON-only workflows with no YAML involvement.

YAML 1.2 ↔ JSON Conversion

Overview

Conformance: 100% of JSON-testable cases — 373 of 402 total (279 valid + 94 error). The remaining 29 cases exercise YAML features with no JSON equivalent.

The YAML converter operates as a zero-allocation ref struct tokenizer on UTF-8 bytes, streaming tokens directly into a Utf8JsonWriter.

Two Packages

PackagePurpose
Corvus.Text.Json.YamlFull Corvus integration — returns ParsedJsonDocument<T>
Corvus.Yaml.SystemTextJsonSystem.Text.Json only — writes to Utf8JsonWriter

Basic Usage

YAML → JSON
csharp
// Full Corvus integration — returns ParsedJsonDocument<T>
using ParsedJsonDocument<JsonElement> doc = YamlDocument.Parse<JsonElement>(yamlBytes);
JsonElement root = doc.RootElement;

// System.Text.Json only — returns JsonDocument
JsonDocument doc = YamlDocument.Parse(yamlBytes);

// Get JSON string from YAML
string json = YamlDocument.ConvertToJsonString(yamlBytes);
JSON → YAML
csharp
// Convert a JSON element to a YAML string (static method on YamlDocument)
string yaml = YamlDocument.ConvertToYamlString(jsonElement);

// Convert to YAML, writing to an IBufferWriter<byte>
YamlDocument.ConvertToYaml(jsonElement, bufferWriter);

// Convert to YAML, writing to a Stream
YamlDocument.ConvertToYaml(jsonElement, utf8Stream);
KYAML output

KYAML (Kubernetes KEP-5295) is a strict subset of YAML 1.2: explicit { } / [ ] delimiters laid out across indented lines, string values always double-quoted, numbers/ booleans/null bare, keys quoted only when ambiguous, trailing comma after every element. Output is always valid YAML 1.2 (read it back with YamlDocument.Parse, no config needed).

Enable it on any ConvertToYaml* overload (or Utf8YamlWriter) via the options:

csharp
// Preset (easiest):
string kyaml = YamlDocument.ConvertToYamlString(json, YamlWriterOptions.Kyaml);

// Or set the format explicitly:
var options = new YamlWriterOptions { Format = YamlWriterFormat.Kyaml };

Implemented entirely in Utf8YamlWriter (gated on YamlWriterFormat.Kyaml); the JSON→YAML converter is format-agnostic. Output is canonical (non-"cuddled") KYAML.

Schema Modes

Four YAML schema modes control how scalar values are interpreted:

ModeDescription
CoreYAML 1.2 Core Schema (default)
JSONJSON-compatible — strings, numbers, booleans, null only
FailsafeAll scalars as strings
Yaml11YAML 1.1 compatibility (yes/no/on/off booleans, sexagesimal integers, merge keys)

Features

  • Anchors & aliases: Full support for &anchor and *alias references
  • Multi-document streams: Processes --- / ... document boundaries
  • Block & flow styles: All YAML block and flow collection styles
  • Tag resolution: %TAG directives, standard !! tags, custom tags

Running Tests

powershell
dotnet test --project tests\Corvus.Text.Json.Yaml.Tests --filter "TestCategory!=failing&TestCategory!=outerloop"

Key Implementation Details

These are important if you're modifying the YAML converter:

  • FinishAnchor: Must not clear _activeAnchorNameStart when hasAnchor=false
  • Block scalars: Must check for document markers (---/...) at column 0
  • %TAG !! redefinition: Makes !!name tags non-standard
  • Float normalization: Written via Utf8Parser + WriteNumberValue for consistent output

Common Pitfalls

  • Encoding: The tokenizer expects UTF-8 bytes. Pass ReadOnlySpan<byte> for best performance.
  • Multi-document: A YAML stream may contain multiple documents. The converter handles them, but the consumer must be aware.
  • Scalar resolution: In Core schema mode, strings like true, false, null, and numbers are auto-resolved. Use Failsafe mode to keep everything as strings.

Cross-References

  • For parsed document handling, see corvus-parsed-documents-and-memory
  • For building/testing, see corvus-build-and-test
  • Full guide: docs/Yaml.md

© corvus-dotnet, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .github/skills/corvus-yaml of corvus-dotnet/Corvus.JsonSchema.

Open the folder on GitHubat commit b9e3040

Compare with similar skills

Corvus YAML next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Corvus YAML compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Corvus YAML this skillcorvus-dotnet/Corvus.JsonSchema199—~1.2kAutomated safety check: PassApache-2.0
Emcaklofas/kicad-happy1.4k1 repos~2.8kAutomated safety check: PassMIT
Swig Testswig/swig6.3k—~2.3kAutomated safety check: PassCustom licence
Generate Test Cases342164796/generate-test-cases1191 repos~2.9kAutomated safety check: PassNone
Verify Cc Safety Netkenryu42/cc-safety-net1.6k—~2kAutomated safety check: PassMIT
Wioworkersio/skills190—~5.8kAutomated safety check: PassMIT

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Categories

Questions about Corvus YAML

What does Corvus YAML do?

Convert between YAML 1.2 and JSON using the high-performance ref struct tokenizer. JsonSchema.2 and JSON using the high-performance ref struct tokenizer.

When should I use Corvus YAML?

Corvus YAML fits situations like: : YAML-to-JSON conversion; JSON-to-YAML conversion; understanding the tokenizer architecture; troubleshooting YAML parsing issues.

How do I install Corvus YAML in Claude Code?

Run `npx skills add corvus-dotnet/Corvus.JsonSchema --skill corvus-yaml -a claude-code`. Or copy the skill folder (.github/skills/corvus-yaml in corvus-dotnet/Corvus.JsonSchema) into .claude/skills/corvus-yaml in your project. Claude Code loads it when a task matches its description.

How do I install Corvus YAML in Codex?

Run `npx skills add corvus-dotnet/Corvus.JsonSchema --skill corvus-yaml -a codex`. Or copy the skill folder (.github/skills/corvus-yaml in corvus-dotnet/Corvus.JsonSchema) into .agents/skills/corvus-yaml in your project. Codex loads it when a task matches its description.

Can I use Corvus YAML in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add corvus-dotnet/Corvus.JsonSchema --skill corvus-yaml -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/corvus-yaml, .gemini/skills/corvus-yaml, .github/skills/corvus-yaml and .opencode/skills/corvus-yaml in your project.

What does Corvus YAML need to run?

Going by SKILL.md and its folder, Corvus YAML needs the command-line tools its instructions call (dotnet).

Does Corvus YAML access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Corvus YAML safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Corvus YAML use?

Corvus YAML is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Corvus YAML use?

About 1.2k tokens (SKILL.md is roughly 4.7k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Corvus YAML?

Skills that share tags, products or a category with Corvus YAML: Emc (aklofas/kicad-happy, 1.4k stars), Swig Test (swig/swig, 6.3k stars), Generate Test Cases (342164796/generate-test-cases, 119 stars) and Verify Cc Safety Net (kenryu42/cc-safety-net, 1.6k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Corvus YAML?

corvus-dotnet (a GitHub organization) maintains it in corvus-dotnet/Corvus.JsonSchema, which has 199 GitHub stars. The repository holds 26 skills in this directory. The repository was last updated on October 8, 2026.

Source: corvus-dotnet/Corvus.JsonSchema on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.