emby-mcp/docs/api/endpoint_validation.md

Emby endpoint conformance audit

This audit compares every upstream REST call made by internal/emby with the Emby Server REST API OpenAPI document, version 4.10.0.40, in emby_openapi.yaml. It is a static check of paths, methods, parameters, request bodies, decoded response fields, and enum values; it does not contact a live Emby server.

Run it with:

go test ./internal/emby/ -run TestSpecConformance -v

Inventory

The manifest contains 34 call sites. ✓ means the call is clean against the spec; ⚠ means it passes through a documented known issue.

#	MCP tool(s)	Call site	Method and path	Operation ID	Status
1	startup auth	library.go:19	POST /Users/AuthenticateByName	postUsersAuthenticatebyname	✓
2	shutdown	library.go:33	POST /Sessions/Logout	postSessionsLogout	✓
3	retrieve_user_list	users.go:20	GET /Users/{Id}	getUsersById	✓
4	retrieve_user_list	users.go:25	GET /Users/Public	getUsersPublic	✓
5	retrieve_library_list, select_library	library.go:39	GET /Library/MediaFolders	getLibraryMediafolders	✓
6	retrieve_genre_list	library.go:58	GET /Genres	getGenres	✓
7	search_for_item, retrieve_next_episode (series resolve)	items.go:135	GET /Users/{UserId}/Items	getUsersByUseridItems	⚠
8	retrieve_item_children	shows.go:28	GET /Users/{UserId}/Items	getUsersByUseridItems	⚠
9	retrieve_season_list	shows.go:48	GET /Shows/{Id}/Seasons	getShowsByIdSeasons	⚠
10	retrieve_episode_list	shows.go:75	GET /Shows/{Id}/Episodes	getShowsByIdEpisodes	⚠
11	retrieve_next_episode (next_unplayed)	shows.go:97	GET /Shows/NextUp	getShowsNextup	⚠
12	retrieve_next_episode (latest)	shows.go:120	GET /Shows/{Id}/Episodes	getShowsByIdEpisodes	⚠
13	retrieve_playlist_list, create_playlist, modify_playlist_name	playlists.go:76	GET /Users/{UserId}/Items	getUsersByUseridItems	✓
14	retrieve_playlist_list	playlists.go:99	GET /Users/ItemAccess	getUsersItemaccess	⚠
15	retrieve_playlist_items	playlists.go:120	GET /Playlists/{Id}/Items	getPlaylistsByIdItems	⚠
16	create_playlist	playlists.go:175	POST /Playlists	postPlaylists	✓
17	modify_playlist_name, create_playlist (overview)	playlists.go:211	GET /Users/{UserId}/Items/{Id}	getUsersByUseridItemsById	✓
18	modify_playlist_name, create_playlist (overview)	playlists.go:223	POST /Items/{ItemId}	postItemsByItemid	✓
19	add_items_to_playlist, create_playlist	playlists.go:230	POST /Playlists/{Id}/Items	postPlaylistsByIdItems	✓
20	remove_items_from_playlist	playlists.go:242	POST /Playlists/{Id}/Items/Delete	postPlaylistsByIdItemsDelete	✓
21	reorder_items_on_playlist	playlists.go:248	POST /Playlists/{Id}/Items/{ItemId}/Move/{NewIndex}	postPlaylistsByIdItemsByItemidMoveByNewindex	✓
22	share_playlist_public	playlists.go:257	POST /Items/{Id}/MakePublic	postItemsByIdMakepublic	✓
23	stop_sharing_playlist	playlists.go:259	POST /Items/{Id}/MakePrivate	postItemsByIdMakeprivate	✓
24	share_playlist_user_access	playlists.go:269	POST /Items/Access	postItemsAccess	✓
25	retrieve_player_list	sessions.go:41	GET /Sessions	getSessions	✓
26	retrieve_player_queue	sessions.go:146	GET /Sessions/PlayQueue	getSessionsPlayqueue	✓
27	retrieve_now_playing, set_subtitle, set_audio_track	sessions.go:183	GET /Sessions	getSessions	✓
28	set_subtitle, set_audio_track	sessions.go:202	POST /Sessions/{Id}/Command	postSessionsByIdCommand	✓
29a	control_media_player (PlayNow)	sessions.go:260	POST /Sessions/{Id}/Playing	postSessionsByIdPlaying	⚠
29b	set_subtitle, set_audio_track (restart fallback)	sessions.go:227	POST /Sessions/{Id}/Playing	postSessionsByIdPlaying	⚠
30	control_media_player (other commands)	sessions.go:281	POST /Sessions/{Id}/Playing/{Command}	postSessionsByIdPlayingByCommand	✓
31	retrieve_now_playing, set_subtitle, set_audio_track	items.go:165	GET /Users/{UserId}/Items/{Id}	getUsersByUseridItemsById	⚠
32	http auth (token→user)	sessions.go:121	GET /Sessions	getSessions	✓
33	http auth (X-Emby-User-Id)	users.go:42	GET /Users/{Id}	getUsersById	✓
34	startup check (http)	system.go:16	GET /System/Info/Public	getSystemInfoPublic	✓

Findings

1. SPEC-GAP — GET /Users/ItemAccess does not declare ItemId

The Go client sends ItemId to restrict the access lookup to the current playlist, but the OpenAPI operation lists only IsHidden, IsDisabled, StartIndex, Limit, NameStartsWithOrGreater, and SortOrder. The upstream Python implementation contains a hotfix that adds item_id to this exact request, which is independent evidence that the server endpoint accepts it.

The test allowlists the missing parameter and fails if the spec later declares it without the registry being updated. Client behavior is unchanged.

2. CODE-DEVIATION — PlayNow sends PlayCommand in the JSON body

For POST /Sessions/{Id}/Playing, the client sends playRequest{PlayCommand, ControllingUserId}. The spec’s PlayRequest schema contains ControllingUserId, SubtitleStreamIndex, AudioStreamIndex, MediaSourceId, and StartIndex, but not PlayCommand. ItemIds and PlayCommand are correctly sent as required query parameters.

This is report-only. A later cleanup could remove PlayCommand from the body struct; no client behavior is changed by this audit.

3. SPEC-QUIRK — MediaStream.Extradata spelling

The spec spells the subtitle payload property Extradata; Emby JSON emits ExtraData. Go’s case-insensitive JSON field matching means the existing ExtraData field still decodes the server value. The spelling is therefore documented as a spec quirk rather than treated as a client defect.

4. SPEC-QUIRK — PlayNow ItemIds is typed as array<int64>

The /Sessions/{Id}/Playing operation describes ItemIds as an integer array, while its description says the values are comma-delimited and real Emby item IDs are strings. The client sends the expected comma-separated string query value. The test keeps a stale guard for this spec shape and does not alter the client encoding.

5. SPEC-GAP — PlayRequest omits StartPositionTicks

PlayNowWithOptions sends StartPositionTicks so set_subtitle / set_audio_track can restart playback at the current position when a session cannot switch streams mid-playback. The spec’s PlayRequest schema omits the field, but Emby has accepted it historically (it is present in real clients’ play requests). The field is allowlisted; the stale guard fails if the spec later declares it.

6. SPEC-GAP — /Shows/{Id}/Episodes has no response schema

The operation declares parameters but no JSON 200-response schema, so the episode-list rows cannot be field-checked. The sibling /Shows/{Id}/Seasons operation returns QueryResult_BaseItemDto, which is what the client decodes. The gap is allowlisted; respField checks are skipped for these rows.

7. SPEC-GAP — /Users/{UserId}/Items/{Id} omits Fields/EnableUserData

GetItem sends both parameters to fetch media streams and per-user watch state for retrieve_now_playing; the spec’s parameter list does not declare them. Real Emby accepts them (they are standard item-query params). The parameters are allowlisted.

Known-issues registry

The registry lives in internal/emby/spec_conformance_test.go. Each entry has a machine-checkable predicate. The test fails on an unexpected violation and also fails when a known issue’s predicate no longer holds, forcing the entry to be removed or revised after a spec/client update.

ID	Kind	Evidence	Action
SPEC-GAP-ITEMACCESS-ITEMID	spec-gap	Python hotfix Emby.MCP/hotfixes/emby/user_service_api.py adds item_id to GET /Users/ItemAccess.	Allowlist; keep client behavior.
CODE-DEVIATION-PLAYREQUEST-PLAYCOMMAND	code-deviation	internal/emby/sessions.go:168 includes PlayCommand; PlayRequest omits it.	Report only; consider a later cleanup.
SPEC-QUIRK-MEDIASTREAM-EXTRADATA	spec-quirk	Spec has Extradata; server JSON/client field uses ExtraData.	Document only.
SPEC-QUIRK-PLAYING-ITEMIDS-TYPE	spec-quirk	Spec says array<int64> but describes comma-delimited IDs; client sends strings.	Document only; retain string query encoding.
SPEC-GAP-PLAYREQUEST-STARTPOSITIONTICKS	spec-gap	playRequest{StartPositionTicks} sent by PlayNowWithOptions; PlayRequest omits it. Real Emby accepts it for resume-position restarts.	Allowlist; keep client behavior.
SPEC-GAP-EPISODES-RESPONSE-SCHEMA	spec-gap	GET /Shows/{Id}/Episodes has no JSON 200-response schema (sibling Seasons returns QueryResult_BaseItemDto).	Allowlist; response fields unchecked on those rows.
SPEC-GAP-ITEMBYID-USERDATA-PARAMS	spec-gap	GET /Users/{UserId}/Items/{Id} omits Fields/EnableUserData params, which real Emby accepts.	Allowlist; keep client behavior.

Scope and adjacent endpoints

The manifest records the parameter names the client may send, including optional parameters that are conditional at runtime. The test does not require the client to send every optional parameter in the spec. The authentication header is also out of the manifest because Client.do adds X-Emby-Authorization to every request centrally.

The spec contains adjacent endpoints that are not used by this client:

• DELETE /Playlists/{Id}/Items exists alongside the client’s POST /Playlists/{Id}/Items/Delete removal call; both are present in the spec.
• POST /Sessions/Playing is a playback check-in endpoint and is not used; the client uses the session-control endpoints under /Sessions/{Id}/Playing.

The YAML and JSON copies should remain synchronized. At audit time their SHA256 hashes were:

emby_openapi.yaml  7738d8eefadad7a2646781a7907fdd0373348fe19ae856d3f6f69dfc2987f27f
emby_openapi.json  55bc60c71b3d5df30d772f7ec4496e0e3f3fa371947691eeb62829a4ea91d530

They are different serializations/copies rather than byte-identical files, so changes to one should be reviewed against the other.