MCP Server | Captain Docs

Connect to the hosted server at https://mcp.captain.dev/mcp: nothing to install, nothing to keep updated.

Connect

Pick your coding agent below and paste in your API key. The command updates to match.

Your Captain API key

Stays in this browser tab, used only to fill in the command below. No key yet? Get one at captain.dev.

claude mcp add --transport http captain https://mcp.captain.dev/mcp \
  --header "Authorization: Bearer cap_..."

Try it

Once the server is connected, talk to your agent normally:

> Search runcaptain-docs for how to retrieve scientific documents as markdown
> Index https://example.com/reports/q4.pdf into finance-docs
> Index this YouTube video into training: https://youtube.com/watch?v=...
> Save this to runcaptain-notes: Decided Lambda over CF Worker. NCBI doesn't IP-rate-limit
> What did we decide about PubMed proxying?

What you get

48 tools, grouped below by what they do. Every tool name is clickable in most MCP clients’ tool pickers; this table is the same information laid out for scanning.

Search and collections

Tool	What it does
`captain_search`	Deterministic File Search over a collection.
`captain_search_v3`	Multimodal search with metadata filters, regions, and relations.
`captain_list_collections`	List collections in the organization.
`captain_create_collection`	Create a collection.
`captain_delete_collection`	Delete a collection.
`captain_copy_collection`	Clone a collection with its vectors branched server-side; returns immediately no matter how large the collection is.
`captain_list_documents`	List documents in a collection.
`captain_delete_document`	Delete a single document.
`captain_wipe_documents`	Delete every document in a collection.

Indexing

Tool	Source
`captain_index_url`	A web URL
`captain_index_youtube`	A YouTube video’s captions (timestamped transcript, not frames or audio; a video without a caption track can’t be indexed this way, index the video file itself for picture and sound)
`captain_index_text`	Inline plain text
`captain_index_file`	An uploaded file
`captain_index_s3`	AWS S3
`captain_index_gcs`	Google Cloud Storage
`captain_index_azure`	Azure Blob Storage
`captain_index_r2`	Cloudflare R2
`captain_index_dropbox`	Dropbox
`captain_index_supabase`	Supabase Storage
`captain_index_backblaze`	Backblaze B2
`captain_index_sharepoint`	SharePoint
`captain_index_onedrive`	OneDrive
`captain_index_gdrive`	Google Drive

Syncs

A sync keeps a collection aligned with a cloud-storage bucket: it backfills, reconciles on a schedule, can listen for real-time events, and propagates deletions.

Tool	What it does
`captain_create_s3_sync`	Create an S3 sync
`captain_create_r2_sync`	Create an R2 sync
`captain_create_supabase_sync`	Create a Supabase sync
`captain_create_backblaze_sync`	Create a Backblaze sync
`captain_list_syncs`	List syncs, across all storage types
`captain_get_sync`	Get one sync’s details
`captain_update_sync`	Update a sync’s config
`captain_delete_sync`	Delete a sync
`captain_reconcile_sync`	Run an on-demand diff and index
`captain_subscribe_sync_webhook`	Subscribe to real-time S3 events

Chunks

Tool	What it does
`captain_list_chunks`	List a document’s chunks
`captain_get_chunk`	Get one chunk
`captain_get_chunk_metadata`	Read a chunk’s custom metadata
`captain_set_chunk_metadata`	Overwrite a chunk’s custom metadata
`captain_update_chunk_metadata`	Merge into a chunk’s custom metadata
`captain_delete_chunk_metadata`	Delete a chunk’s custom metadata
`captain_list_chunk_relations`	List relations between chunks
`captain_create_chunk_relation`	Create a relation between chunks
`captain_delete_chunk_relation`	Delete a relation

Jobs

Tool	What it does
`captain_job_status`	Check an indexing job’s status
`captain_cancel_job`	Cancel an in-progress job

Environments

Tool	What it does
`captain_change_environment`	Move a collection between development, staging, and production

API keys are scoped to one environment (cap_dev_ keys see development, cap_stage_ staging, cap_prod_ production), so a moved collection leaves behind the keys of the environment it came from, and attached syncs do not follow it.

Project notes

Tool	What it does
`captain_save`	Write a short note (a decision, a gotcha, a bug repro, a design constraint) to a per-project collection under a timestamped filename, creating the collection on first use
`captain_find`	Search those notes; surfaces the timestamps, so a stale note is easy to spot

Integration wizard

captain_wizard writes Captain into your codebase. It reads Captain’s own agent docs at llms.txt as the source of truth for the current API surface, covering indexing calls, search wiring, collection setup, and auth, then applies the changes for a task you describe. The first time you run it, it asks permission to send de-identified feedback about the integration (friction, missing capabilities, confusing docs) to Captain’s feedback endpoint. No API key, no code, no personal data. Decline it if you prefer, and change the answer later at any time.

Local install (deprecated)

The local stdio build (npx @captain-sdk/captain-mcp) is deprecated and no longer maintained. New tools and fixes ship only to the hosted server, so local installs will fall behind. The one thing it still does that the hosted server cannot is let captain_index_file read local filesystem paths. The hosted server takes urls or inline base64 files instead.

If you still need it, your client launches it with npx and it reads CAPTAIN_API_KEY from the environment:

1 {
2   "mcpServers": {
3     "captain": {
4       "command": "npx",
5       "args": ["-y", "@captain-sdk/captain-mcp@latest"],
6       "env": { "CAPTAIN_API_KEY": "cap_..." }
7     }
8   }
9 }