Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add agentfront/frontmcp --skill frontmcp-extensibilitygit clone --depth 1 https://github.com/agentfront/frontmcpWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/agentfront/frontmcp/frontmcp-extensibility)<a href="https://agentmods.dev/skills/agentfront/frontmcp/frontmcp-extensibility"><img src="https://agentmods.dev/badge/skills/agentfront/frontmcp/frontmcp-extensibility/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/agentfront/frontmcp/frontmcp-extensibility"><img src="https://agentmods.dev/badge/skills/agentfront/frontmcp/frontmcp-extensibility.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 7 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Prompt Injection · line 128 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Prompt Injection · line 141 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Prompt Injection · line 141 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Memory Poisoning · line 152 Skill attempts to fill the context window with filler content, displacing legitimate instructions and safety constraints. This can degrade agent performance or bypass safety boundaries.Fix: Implement context-window management that detects and rejects padding or stuffing attempts. Prioritize system instructions over user-injected content.
- medium Prompt Injection · line 152 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Prompt Injection · line 154 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Prompt Injection · line 155 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00124 | $0.02365 |
| Opus 5.5 | $0.00050 | $0.00946 |
| Sonnet 5.5 | $0.00025 | $0.00473 |
| Haiku 4.5 | $0.00012 | $0.00236 |
Grade A, and why
frontmcp-extensibility scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 164 lines — stays where its author put it; the contents beside it link to each section on GitHub.
FrontMCP Extensibility
Patterns and examples for extending FrontMCP servers with external npm packages. The core SDK handles MCP protocol, DI, and lifecycle — this skill shows how to integrate third-party libraries as providers and tools.
When to Use This Skill
Must Use
- Adding semantic search or similarity matching to your server (VectoriaDB)
- Integrating an external npm package as a FrontMCP provider
- Building tools that wrap third-party services (databases, APIs, ML models)
Recommended
- Looking for patterns to structure external service integrations
- Deciding between provider-based vs direct integration for a library
- Adding capabilities like applescript automation, VM execution, or data processing
Skip When
- You need to build core MCP components (see
frontmcp-development) - You need to configure auth, transport, or CORS (see
frontmcp-config) - You need to write a plugin with hooks and context extensions (see
create-plugin)
Decision: Use this skill when integrating external libraries into your FrontMCP server as providers or tools.
Prerequisites
- A FrontMCP project (see
frontmcp-setupif you don't have one). - The external library installed as a runtime
dependency(notdevDependency). - Familiarity with FrontMCP providers and tools (see
create-provider,create-tool).
Steps
- Pick the integration shape — provider for stateful clients (DB, search index), tool-only for stateless one-shot calls.
- Wrap the library in a provider — declare a typed DI token and a
@Providerclass so consumers depend on the boundary, not the library. - Register it — add to
@App({ providers: [...] })or@FrontMcp({ providers: [...] }). - Expose via tools/resources — call
this.get(TOKEN)inToolContext/ResourceContext; never import the library directly from the tool. - Handle errors at the boundary — translate library-specific errors into
PublicMcpError/InvalidInputErrorso MCP clients see structured failures.
What ships with it
7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
- examples/skill-audit-log/custom-store.md 7.4 KB
- examples/skill-audit-log/verify-chain.md 3.3 KB
- examples/vectoriadb/product-catalog-search.md 5.4 KB
- examples/vectoriadb/semantic-search-with-persistence.md 4.4 KB
- examples/vectoriadb/tfidf-keyword-search.md 3.5 KB
- references/skill-audit-log.md 20 KB
- references/vectoriadb.md 12 KB
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 10d ago Changed f118af3ab55f
- 15d ago Changed 82ba763ec1b5
- 1mo ago First seen · 164 lines · 124 tokens per session scan A 4f603138ce45
frontmcp-extensibility is a skill published in the GitHub repository agentfront/frontmcp (147 stars, last pushed today), licensed Apache-2.0. It adds 124 tokens to every session and 2,365 once invoked, about $0.0005 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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