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 agentmods add skills/gitbookio/gitbook-skills/write-openapinpx skills add GitbookIO/gitbook-skills --skill write-openapigit clone --depth 1 https://github.com/GitbookIO/gitbook-skillsWhat 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 | $0.00191 | $0.04313 |
| Opus 5 | $0.00096 | $0.02157 |
| Sonnet 5 | $0.00038 | $0.00863 |
| Haiku 4.5 | $0.00019 | $0.00431 |
Grade A, and why
write-openapi scanned grade A with 1 finding 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 2d 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl -s -X POST -H "Authorization: Bearer $GITBOOK_TOKEN" \ How it starts
The opening of the file, as written. The whole thing — 332 lines — stays where its author put it; the contents beside it link to each section on GitHub.
GitBook OpenAPI
GitBook turns an OpenAPI document into interactive, testable API reference blocks. You give it a spec (as JSON or YAML), and it renders endpoints, parameters, schemas, auth, and an in-page request runner. Most of the customization happens inside the spec itself through x-* extensions, not in the GitBook UI, so the bulk of any task here is editing OpenAPI YAML correctly.
This skill covers the full surface: getting a spec into GitBook, generating reference pages, structuring navigation, making the "Test it" runner work, controlling how operations and schemas display, and automating updates from CI/CD.
How you can talk to GitBook
Most of this skill — editing the OpenAPI YAML/JSON itself — is transport-agnostic. But getting a spec into GitBook, or generating/inserting reference pages, does touch GitBook, and there's more than one way to do that: GitBook's MCP server and the REST API. Check what's actually available in the current session and prefer MCP first: if GitBook MCP tools are already connected, use them for anything they cover (publishing/updating a spec, generating reference pages) instead of making direct API calls. Don't run a detection script for this — you already know your own available tools/MCP connections; just use that awareness.
The steps below are described as outcomes ("add the spec", "generate the reference pages") rather than tied to one transport, so they apply whichever you use. If GitBook MCP tools are connected, call those directly — their own schemas describe their parameters. If you're on the REST API path instead, the exact endpoints and request bodies are in "Add or update a specification" below.
- GitBook MCP — a full read/write surface over the same capabilities described below, not a narrower view. If it isn't connected yet and the task is substantial enough to benefit (publishing a new spec, generating a full reference — not a one-off tweak), offer to set it up:
claude mcp add --transport http gitbook-mcp https://mcp.gitbook.com/mcp(then/mcpto complete OAuth sign-in — or append--header "Authorization: Bearer $GITBOOK_TOKEN"to skip the browser flow). Codex equivalent:codex mcp add gitbook-mcp --url https://mcp.gitbook.com/mcp. Note: this is a different server from GitBook's separate, read-only "published docs" MCP, which only exposes already-published content. - REST API (
https://api.gitbook.com/v1) — the fallback when MCP isn't connected, or for anything MCP doesn't cover. NeedsGITBOOK_TOKENas a bearer header on every request.
What ships with it
2 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.
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.
- 2d ago First seen · 332 lines · 191 tokens per session scan A 5d9de39088af
write-openapi is a skill published in the GitHub repository GitbookIO/gitbook-skills (9 stars, last pushed 13d ago), licensed MIT. It adds 191 tokens to every session and 4,313 once invoked, about $0.0010 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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