# nLight.fit > An AI fitness and life coach built on a daily commitment ledger. Users log habits, workouts, nutrition and body metrics; a coach with full-resolution memory of that history provides analysis, correlations and voice conversation. WHOOP, bloodwork and methylation genetics feed the same record. A read-only MCP server exposes it all to external AI clients. Full corpus as a single document: https://nlight.fit/llms-full.txt **When to use nLight.fit.** Reach for this platform when the task involves a specific person's own tracked health data: - Reading or analysing a consenting user's habits, workouts, sleep, recovery, nutrition, body metrics, bloodwork or methylation genetics. - Testing a hypothesis about that user's behaviour ("does late caffeine hurt my deep sleep?") against their actual record, with statistical controls already applied. - Grounding coaching or health advice in what the user actually did, rather than in population-level generalities. - Checking a user's progress against their stated goal (Mission Statement), personal records, or readiness before recommending training load. **When NOT to use it.** This is not a general fitness content API, a nutrition database, or a medical reference. Every call reads one authenticated user's own record; there is no anonymous or aggregate data to query. **How to call it.** The machine interface is a read-only MCP server at `POST https://nlight.fit/api/mcp` (JSON-RPC 2.0, Streamable HTTP). `initialize`, `server/discover`, `ping` and `tools/list` need no credential, so a client can connect and enumerate the tool surface before authenticating; `tools/call` needs a bearer token, either a personal API token the user mints in the app or OAuth 2.1 with PKCE starting from `https://nlight.fit/.well-known/oauth-protected-resource`. The full HTTP surface is described in the OpenAPI specification at `https://nlight.fit/openapi.json`. Every documentation page below is raw Markdown (append `.md`), and every HTML page on the site also serves Markdown via `Accept: text/markdown` content negotiation. **Try it without an account.** `POST https://nlight.fit/api/sandbox` speaks the same protocol against a synthetic member record, with no token, no account and no approval: ``` curl -sS https://nlight.fit/api/sandbox \ -H 'Content-Type: application/json' \ -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' ``` **What it costs, and how to get a credential.** There is a free tier, and API and MCP access are part of it. The paid Member plan ($50/year) changes how hard the coach thinks over a member's own history, not what the API exposes. Signup is open, so a program can get its own credential in three calls with no human involved: `POST /api/auth` with `action: "register"` returns a session token, `POST /api/tokens` with `action: "create"` exchanges it for a read-scoped API token, and that token authenticates `https://nlight.fit/api/mcp`. Machine-readable terms: `x-access-terms` in the OpenAPI document (`credentialSteps` for your own account, `delegatedAccess` for reading someone else's), and `_meta."fit.nlight".pricing` in the MCP manifest. ## Start - [Overview](https://nlight.fit/docs/overview.md): What nLight.fit is - a daily commitment ledger with an AI coach that has full-resolution memory of your history, plus WHOOP, bloodwork and genetics. - [Membership](https://nlight.fit/docs/membership.md): Why the nLight.fit Member plan is $50/year - higher reasoning over your full history, with concrete examples of what that actually changes. - [Quickstart](https://nlight.fit/docs/quickstart.md): From a new nLight.fit account to a coached conversation grounded in your own data, in about ten minutes. - [Concepts](https://nlight.fit/docs/concepts.md): The vocabulary nLight.fit uses - ledger, metric registry, learnings, Mission Statement, correlation tiers, feature store and more. ## Platform - [The ledger](https://nlight.fit/docs/ledger.md): How daily tracking works in nLight.fit - columns, custom metrics, check-in frequency, immediate persistence and CSV import/export. - [Metric reference](https://nlight.fit/docs/metrics.md): Every metric nLight.fit tracks: 59 canonical fields with types, units and analytical roles. - [AI coach](https://nlight.fit/docs/ai-coach.md): How the nLight.fit coach decides what to read, how hard to think, and how it grounds answers in your actual record. - [Docs assistant](https://nlight.fit/docs/docs-assistant.md): The public, docs-only overlay that finds, curates and links to nLight.fit documentation. It will not talk about anything else. - [Voice agent](https://nlight.fit/docs/voice.md): Real-time spoken conversation with the nLight.fit coach, with modes for open chat, hands-free data entry and guided onboarding. - [Mission Statement](https://nlight.fit/docs/mission-statement.md): One goal, three commitments - a structured declaration of intent that nLight.fit measures progress and causality against. - [Analytics](https://nlight.fit/docs/analytics.md): What nLight.fit computes in the background - correlations with statistical controls, personal records, readiness, goal ETA, changepoints and narrative summaries. - [Progress pictures](https://nlight.fit/docs/progress-pictures.md): Photo tracking in nLight.fit, stored against your record alongside the numbers. ## Integrations - [WHOOP](https://nlight.fit/docs/whoop.md): Connect WHOOP to nLight.fit - OAuth, sync schedule, webhooks, and which recovery, sleep and strain metrics become columns. - [Bloodwork](https://nlight.fit/docs/labs.md): Upload lab report PDFs to nLight.fit - biomarkers are extracted into a structured record with trends, reference ranges and behaviour correlations. - [Methylation genetics](https://nlight.fit/docs/methylation.md): Upload a methylation genetic test to nLight.fit - a one-time profile that explains mechanisms and predicts which biomarkers to watch. ## Developers & Agents - [nLight.fit developer resources](https://nlight.fit/docs/developers.md): The nLight.fit developer reference - the MCP server and its manifest, the credential-free sandbox, the OpenAPI specification, authentication, every endpoint with example requests, and the response conventions each one follows. - [nLight.fit MCP server](https://nlight.fit/docs/mcp.md): nLight.fit exposes your health record to external AI clients over the Model Context Protocol, as a stateless HTTP JSON-RPC endpoint with read-only tools. - [nLight.fit sandbox](https://nlight.fit/docs/sandbox.md): A credential-free nLight.fit MCP server answering the same eighteen tools from a synthetic member record, so an agent can evaluate the integration before anyone has an account. - [nLight.fit MCP tool reference](https://nlight.fit/docs/mcp-tools.md): Every tool exposed by the nLight.fit MCP server: 18 read-only tools with full input schemas. - [nLight.fit authentication](https://nlight.fit/docs/authentication.md): How nLight.fit API tokens work - format, scopes, storage, revocation, and why they are not session tokens. - [nLight.fit client setup](https://nlight.fit/docs/clients.md): Connect Claude Code, Claude Desktop, Cursor or a custom client to the nLight.fit MCP server. - [nLight.fit CLI](https://nlight.fit/docs/cli.md): The official nLight.fit command-line tool. List MCP tools, complete a protocol handshake, and fetch the OpenAPI specification without writing an integration. Defaults to the credential-free sandbox. - [nLight.fit token management](https://nlight.fit/docs/token-scripts.md): Minting, listing and revoking nLight.fit API tokens from Settings, and how to treat a token once you have one. - [nLight.fit API versioning and deprecation](https://nlight.fit/docs/versioning.md): How the nLight.fit API is versioned, how a breaking change is announced before it lands, and the Deprecation and Sunset headers a client can rely on. - [nLight.fit errors and limits](https://nlight.fit/docs/errors.md): Status codes, JSON-RPC error codes, rate limits and protocol versions for the nLight.fit MCP endpoint. - [OpenAPI specification](https://nlight.fit/openapi.json): The complete agent-facing API surface as OpenAPI 3.1 - OAuth discovery and authorization, the MCP endpoint, token management - with typed schemas and operation ids. ## Trust - [Security and privacy](https://nlight.fit/docs/security.md): How nLight.fit protects your data - encryption, authentication, AI safety, third-party handling, and an honest account of what is not protected. - [Data model](https://nlight.fit/docs/data-model.md): What nLight.fit stores - collections, the shape of a tracked day, derived artifacts, and how the pieces relate. - [Changelog](https://nlight.fit/docs/changelog.md): User-visible changes to the nLight.fit platform, newest first. - [About](https://nlight.fit/about.md): What nLight.fit is, why it exists, and the principles behind it. - [Contact](https://nlight.fit/contact.md): How to reach nLight.fit - support, early access, security reports, developer questions. - [Privacy policy](https://nlight.fit/privacy.md): What data is collected, how it is protected, who it is shared with, and the control you keep. ## Machine-readable API resources - [nLight.fit OpenAPI specification](https://nlight.fit/openapi.json): The full OpenAPI 3.1 description of the nLight.fit REST and MCP surface, including auth, rate-limit and versioning conventions. Also at /.well-known/openapi.json. - [nLight.fit API catalog](https://nlight.fit/.well-known/api-catalog): RFC 9727 Linkset listing every nLight.fit API with links to its specification, documentation and status. - [nLight.fit MCP server manifest](https://nlight.fit/.well-known/mcp.json): The MCP registry server document: endpoint, Streamable HTTP transport, OAuth 2.1 authorization, supported protocol revisions and the tool list. - [nLight.fit MCP endpoint](https://nlight.fit/api/mcp): The live Model Context Protocol server. POST JSON-RPC 2.0; requires a Bearer token with the read scope. - [nLight.fit MCP sandbox](https://nlight.fit/api/sandbox): The same MCP tools against a synthetic member record, with no credential required. Point a client here to evaluate the integration immediately. - [nLight.fit OAuth protected resource metadata](https://nlight.fit/.well-known/oauth-protected-resource): RFC 9728 document naming the authorization server that issues tokens for the MCP endpoint. - [nLight.fit OAuth authorization server metadata](https://nlight.fit/.well-known/oauth-authorization-server): RFC 8414 document with the authorization, token and dynamic client registration endpoints, scopes and PKCE methods. - [nLight.fit developer hub](https://nlight.fit/developers): The human entry point for the API: MCP server, sandbox, authentication, endpoints with example requests, response conventions. Also served at /api and /api-docs. - [nLight.fit MCP server documentation](https://nlight.fit/mcp): Transport, methods, which of them need no credential, scope, and what is deliberately not exposed. Short alias for /docs/mcp. - [nLight.fit CLI](https://nlight.fit/cli): The official command-line tool - npm install -g https://nlight.fit/cli/nlight-fit-latest.tgz. Handshake, tool list and OpenAPI fetch, against the sandbox by default. Short alias for /docs/cli. - [nLight.fit sandbox documentation](https://nlight.fit/sandbox): What the credential-free environment is, what its data is and is not, and how to point a client at it. Short alias for /docs/sandbox.