Over HTTP¶

The same server runs on its own beside After Effects and serves several clients over Streamable HTTP. Each client presents a key of its own, which names it and says what it may do.

Starting it¶

mkdir -p ~/.config/s3l-mcp-aftereffects
echo '{ "Snail": { "Http": { "Token": "<a long random secret>" } } }' > ~/.config/s3l-mcp-aftereffects/config.json
chmod 600 ~/.config/s3l-mcp-aftereffects/config.json
export SNAIL_MCP_AFTEREFFECTS_TRANSPORT=Http
export SNAIL_MCP_AFTEREFFECTS_HTTP__URL=http://0.0.0.0:8080
dotnet Snail.MCP.AfterEffects.dll clients add titles --scope read,write,farm
dotnet Snail.MCP.AfterEffects.dll

The server refuses to start without a token: it would turn every client away while looking healthy. The token is the operator's key and holds every scope; clients add mints a key per client, printed once, and clients list and clients revoke <name> manage them. A revoked key is turned away on its next request, without restarting the server.

Kept running by launchd¶

A server that is meant to be there whenever After Effects is runs as a job of this Mac, not from a terminal. The template is deploy/s3l.mcp.aftereffects.plist; installing writes it with this machine's paths beside the publications:

dotnet publish src -c Release -p:Install=true

The install restarts the job when launchd already holds this very one, and otherwise prints the two commands that load it:

launchctl bootstrap gui/$UID ~/.s3l-mcp/Snail.MCP.AfterEffects/s3l.mcp.aftereffects.plist
launchctl kickstart -k gui/$UID/s3l.mcp.aftereffects

The job carries the transport and the address only. The operator's key stays in ~/.config/s3l-mcp-aftereffects/config.json, so no secret is in a file a backup may carry. Its log is ~/Library/Logs/Snail.MCP.AfterEffects.log. After Effects itself is not started by the job: the bridge in its Startup folder dials the server whenever a person opens the application.

Keys and scopes¶

A client connects to /mcp with Authorization: Bearer <key>. The key's scopes are checked before a call reaches After Effects, inside run_tools and run_program too, and over the file endpoints:

Scope	Opens
`read`	reading the project, the files, the diagnostics
`write`	changing the project and writing files
`delete`	removing items, layers and files, undo, cancelling renders, replacing files that exist
`script`	`ae_script`, `ae_run_menu_command`, and the `script` command inside sequences and programs
`farm`	`ae_render`, `ae_render_in_media_encoder`, `ae_farm_submit` and `ae_farm_retry`

A key minted without --scope gets everything but script. The call a key does not open is answered with a refusal naming the scope.

One tool list per client¶

Each client has a tool list of its own: a skill one client loads is in its list and nobody else's, and tools/list_changed reaches the client that holds a session. A client of the sessionless protocol revision is recognised by the name on its key.

Pages and files¶

/ shows the status (After Effects, the bridge, the farm, the storage, the server), and the areas files, captures, renders and jobs with previews, downloads, deletion and the cancelling of a running job; sign in with any key. /healthz answers anyone. /raw/<area>/<path> serves a file, or a folder as a tar or zip, and takes uploads into the files area, with a key or with a signed link that works for HTTP__LINK_MINUTES; ae_upload and ae_download hand such links out as shell commands for the client's machine.