Frontmcp Extensibility

What it does

When your agent uses it

• Extending FrontMCP beyond the core SDK by integrating external npm packages
• Third-party services into providers and tools

Example prompts

• “/frontmcp-extensibility”

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

1. 1Pick the integration shape — provider for stateful clients (DB, search index), tool-only for stateless one-shot calls.
2. 2Wrap the library in a provider — declare a typed DI token and a @Provider class so consumers depend on the boundary, not the library.
3. 3Register it — add to @App({ providers: [...] }) or @FrontMcp({ providers: [...] }).
4. 4Expose via tools/resources — call this.get(TOKEN) in ToolContext/ResourceContext; never import the library directly from the tool.
5. 5Handle errors at the boundary — translate library-specific errors into PublicMcpError/InvalidInputError so MCP clients see structured…

What it can do on your machine

Read from SKILL.md and the folder at commit 8f59ba8. 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

  No scripts in the folder and no shell commands in SKILL.md (its code samples are typescript).

  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

Frontmcp Extensibility loads about 3.2k tokens when it runs, and up to ~10k if it reads all its reference files. Until then it costs about 150 tokens; SKILL.md has 924 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

~3.2k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~10k

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

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 agentfront/frontmcp at commit 8f59ba8, republished under its Apache-2.0 licence (© agentfront). 924 words, ~3,221 tokens.

name

frontmcp-extensibility

description

Use when extending FrontMCP beyond the core SDK by integrating external npm packages, libraries, or third-party services into providers and tools. Covers VectoriaDB for in-memory semantic and vector search (ML-based embeddings or TF-IDF keyword engines, with persistence) and the tamper-evident, hash-chained skill audit log (pluggable signer and store, with chain verification). Triggers: add semantic search, vector search, embeddings, similarity search, recommendations, ML features, audit logging, or integrate an external library, database, or API beyond the built-in SDK.

tags

extensibility, vectoriadb, search, integration, npm, provider, external-services

category

extensibility

targets

all

bundle

full

priority

10

visibility

both

license

Apache-2.0

metadata.docs

https://docs.agentfront.dev/frontmcp/extensibility/providers

// 1. Provider wraps the library (the class itself is the DI token)
@Provider({ name: 'my-search', scope: ProviderScope.GLOBAL })
export class SearchProvider {
  private client: ExternalLibrary;
  constructor() {
    this.client = new ExternalLibrary({
      /* config */
    });
  }
  async search(query: string) {
    return this.client.query(query);
  }
}

// 2. Tool exposes it
@Tool({ name: 'search', inputSchema: { query: z.string() } })
export default class SearchTool extends ToolContext {
  async execute(input: { query: string }) {
    return this.get(SearchProvider).search(input.query);
  }
}

© agentfront, 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

SKILL.md and 7 other files (references) in libs/skills/catalog/frontmcp-extensibility of agentfront/frontmcp.

• SKILL.md
• examples/skill-audit-log/custom-store.md
• examples/skill-audit-log/verify-chain.md
• examples/vectoriadb/product-catalog-search.md
• examples/vectoriadb/semantic-search-with-persistence.md
• examples/vectoriadb/tfidf-keyword-search.md
• references/skill-audit-log.md
• references/vectoriadb.md

Open the folder on GitHubat commit 8f59ba8