tachyon extensions

🧩 tachyon-extensions

Verdict: optional add-ons built only on public SPI. Main piece = Skills extension exposing SKILL.md directories as skill:// resources + skills/list|get + resources/directory/read. Plus sample tools.

🎓 SkillsExtension

tachyon-extensions/src/main/java/dev/tachyonmcp/extensions/skills/SkillsExtension.java

Aspect	Value	Proof
id	io.modelcontextprotocol/skills	SkillsExtension#ID
advertise	ALWAYS, settings {directoryRead: true}	SkillsExtension#advertiseMode, SkillsExtension#serverSettings
_meta envelope	not required	SkillsExtension#requiresMetaEnvelope (fix 582f9c52)
negotiation	builder negotiation(...), default REQUIRED ⇒ undeclared ⇒ missing required client capability: -32003 (2025-11-25), -32021 + HTTP 400 (2026-07-28); base resources/list|read still served. OPTIONAL opt-in serves undeclared clients (e.g. MCP Inspector; same advertisement)	SkillsExtension#negotiation, SkillsExtension.Builder#negotiation; codes in McpResponseMapper (v2025_11_25, v2026_07_28)
bootstrap	every skill file → resource (SKILL.md named by frontmatter name + description); text vs blob by MimeTypes.isText	SkillsExtension#bootstrap, SkillsExtension#contents
methods	skills/list (no pagination; ttlMs, cacheScope), skills/get {uri}, resources/directory/read {uri} (children with inode/directory)	SkillsExtension#listSkills, SkillsExtension#getSkill, SkillsExtension#readDirectory
builder	registry(...), cacheTtlMs ≥ 0, cacheScope public|private	SkillsExtension.Builder

Skill model SkillsRegistry.Skill(skillPath, frontmatter, files), SkillFile(relativePath, uri, mimeType, sha256 digest, size); skillUri = skill://<path>/SKILL.md Skill.

📂 Registries

Impl	Source	Proof
FilesystemSkillsRegistry(root) / (dir, skillPath)	dir of skill dirs / single	FilesystemSkillsRegistry#FilesystemSkillsRegistry
ClasspathSkillsRegistry(resource[, skillPath])	file: or jar: URLs	ClasspathSkillsRegistry
CompositeSkillsRegistry	dup skill path ⇒ IAE	CompositeSkillsRegistry#CompositeSkillsRegistry
BaseSkillsRegistry	dir scan lenient (skip invalid, warn), single strict	BaseSkillsRegistry

Validation SkillsScanner.buildSkill: SKILL.md required, YAML frontmatter (SnakeYAML SafeConstructor) with non-blank name+description, last path segment == name SkillsScanner#buildSkill, FrontmatterParser#parse. Ignore globs from classpath META-INF/dev/tachyonmcp/extensions/skills/.mcpignore (gitignore-ish: anchored /, dir / suffix) IgnoreRules.

🔧 Sample tools

• EchoToolHandler — echo {message} EchoToolHandler.java.
• YouComSearchTool(YouComSearchConfig) — you-search, JDK HttpClient, free tier w/o key, X-API-Key otherwise, structured + text results YouComSearchTool.

🧪 Tests

SkillsExtensionTest, SkillsExtensionE2eTest, registry/parser/ignore tests; fixtures tachyon-extensions/src/test/data/skills/, src/test/resources/skills/. Example app examples/mcp-skills.

Related: extensions.

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_{📄 source .llm-wiki/modules/tachyon-extensions.md · updated 2026-09-15 · verified at 9eec1092 · tags [module, extensions, skills]}