Borrowing it
Nothing to install: this file belongs to webhook-co/webhook. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/webhook-co/webhook/main/.cursor/skills/build-mcpb/SKILL.mdgit clone --depth 1 https://github.com/webhook-co/webhookWrote 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/webhook-co/webhook/build-mcpb)<a href="https://agentmods.dev/skills/webhook-co/webhook/build-mcpb"><img src="https://agentmods.dev/badge/skills/webhook-co/webhook/build-mcpb/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/webhook-co/webhook/build-mcpb"><img src="https://agentmods.dev/badge/skills/webhook-co/webhook/build-mcpb.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00052 | $0.00523 |
| Opus 5.5 | $0.00021 | $0.00209 |
| Sonnet 5.5 | $0.00010 | $0.00105 |
| Haiku 4.5 | $0.00005 | $0.00052 |
Grade A, and why
build-mcpb 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 1mo 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 — 45 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Build MCPB
MCPB packages a local stdio MCP server into a single installable bundle a user can drop into an
MCP host. Use it only when the server must run on the user's machine — the clearest case here is
tooling that rides with the CLI / tunnel client and needs local environment access. For anything
that can run server-side, prefer the remote streamable-HTTP server on Workers (see
build-mcp-server); don't package something as MCPB just to avoid hosting it.
When MCPB is the right call
- The server needs the user's local filesystem, processes, or network position (e.g. replay-to- localhost tooling) that a remote Worker can't reach.
- You want one-step install for a stdio server instead of asking users to clone and wire up a runtime.
If neither is true, it belongs on Workers as a remote server.
Packaging checklist
- The server runs over stdio and starts cleanly with no manual setup beyond the bundle.
- The manifest declares name, version, entry point, and the inputs/secrets it expects — with clear placeholders, never real tokens or account/zone IDs.
- Secrets are requested at install/runtime and read from the environment; nothing sensitive is baked into the bundle.
- Tool contracts and types match the other surfaces (
shared/); the bundle is a packaging of an existing capability, not a divergent one. - Versioning + a smoke test: the bundle installs and the tools respond on a clean machine.
Guardrails
- MCP/AI-native parity: a locally-bundled capability still exists on CLI/API/web/MCP at parity.
- Standard-Webhooks-native signing/verification; no hand-rolled schemes shipped in the bundle.
- Private-by-default and public-safe: no secrets, account/zone IDs, or pricing details in the manifest or bundled code.
- A local server is still subject to the same validation and redaction rules — never log full payloads or PII/PHI.
Progressive disclosure
Keep the manifest template, signing/distribution steps, and a clean-machine install drill in references/.
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.
- 1mo ago First seen · 45 lines · 52 tokens per session scan A b90e1977251c
build-mcpb is a skill published in the GitHub repository webhook-co/webhook (0 stars, last pushed 18d ago), licensed Apache-2.0. It adds 52 tokens to every session and 523 once invoked, about $0.0002 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 2026-08-31.
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