Destination · publishing reference
Facebook Reels publishing reference for Postdom
This Facebook Reels publishing reference explains the configured Reel path, account connection, enforced limits, sent settings, and result boundary.
Human authorization boundary
Facebook Reels publishing reference connection requirements
A human completes the destination connection. The agent receives the resulting account ID—not the social credential—and supplies that exact account ID to publish_video.
connectionOAuth
prerequisiteNo additional Postdom prerequisite is recorded beyond an eligible account.
current source surfacereel, feed, story
Configured output
What Postdom sends to Facebook Reels
The public tool accepts product-level publishing fields. Postdom builds destination settings after validation; callers cannot smuggle an undocumented settings object through publish_video.
surface.facebook- omitted (default) or reel | feed | story (current source)
An omitted surface uses the media-dependent default; video defaults to Reel. This input exists in current source and is separate from released @postdom/mcp@0.4.0.
contentType- reel
Default video output. Current source omits contentType for feed and sends story for Story.
visibility- omitted
Postdom sends no Facebook audience setting; the connected account controls it.
This example is the default video path, not the only current-source path. The released @postdom/mcp@0.4.0 helper maps Facebook video to Reel and exposes no surface override. Current source also accepts surface.facebook as reel, feed, or story and translates that choice for the provider. Neither contract sends a Facebook visibility setting; account-side audience controls remain outside the tool schema.
{
"platform": "facebook",
"settings": {
"contentType": "reel"
}
}Enforced, documented, or unknown
Facebook Reels publishing limits
Every row comes from the current @postdom/core registry. “Postdom enforced” means the source contract checks the fact. A recommendation, documented-but-unenforced fact, or unpublished value must not be presented as a passed validation.
caption max chars
4000
Postdom contract · verified 2026-08-21T00:00:00.000Z
Evidence reference retained in the core registry.
media max bytes
524,288,000 bytes
Postdom contract · verified 2026-08-21T00:00:00.000Z
Evidence reference retained in the core registry.
video max seconds
600
Postdom contract · verified 2026-08-21T00:00:00.000Z
Evidence reference retained in the core registry.
video mime types
video/mp4, video/quicktime
Postdom contract · verified 2026-08-21T00:00:00.000Z
Evidence reference retained in the core registry.
image mime types
image/jpeg, image/png, image/gif, image/webp
Postdom contract · verified 2026-08-21T00:00:00.000Z
Evidence reference retained in the core registry.
reels publishing description
Not published
Unit: not stated · Field: description · Scope: POST /{page-id}/video_reels
Platform evidence · verified 2026-09-03T00:00:00.000Z
Qualification
Meta publishes no maximum for this field, so there is no number to enforce.
video min seconds
3
Platform evidence · verified 2026-09-02T00:00:00.000Z
Official sourcevideo max seconds
90
Platform evidence · verified 2026-09-02T00:00:00.000Z
Official sourcevideo mime types
video/mp4
Platform evidence · verified 2026-09-02T00:00:00.000Z
Official sourceresolution max pixels
Not published
Platform evidence · verified 2026-09-02T00:00:00.000Z
Official sourceresolution recommended
width: 1080; height: 1920
Platform evidence · verified 2026-09-02T00:00:00.000Z
Official sourceaspect ratio recommended
9:16
Platform evidence · verified 2026-09-02T00:00:00.000Z
Official sourceresolution min pixels
width: 540; height: 960
Platform evidence · verified 2026-09-02T00:00:00.000Z
Qualification
Meta's own floor - "Minimum is 540 x 960 pixels" - and the first Facebook resolution fact we hold from Meta rather than from the provider, which published none. Not gated because gating it would add a rejection, and this whole re-sourcing exists because Postdom was rejecting Reels Meta accepts. A floor read off one documentation line can be wrong in the direction that costs a customer a post, so it is recorded and left unread until a request is observed failing on it.
aspect ratio
minimum: 0.5625; maximum: 1.7777777777777777
Platform evidence · verified 2026-09-02T00:00:00.000Z
Qualification
"Aspect ratios for videos need to be between 16x9 and 9x16", from error code 1363040 rather than from the specification table. Taken from the error table deliberately: the spec table lists "9 x 16" as the target, while the error table states what Meta actually rejects, and a rejection contract is the stronger evidence of a bound. The two do not conflict - 9:16 sits at one end of the published range. Recorded as the range rather than the target so a square video is not read as violating a limit Meta does not impose. Not gated: the Facebook preflight branch reads durations only.
Result boundary
How to verify the Facebook Reels outcome
This page describes the current source contract. It does not claim an authenticated Page Reels publication test or guarantee that every platform field is observable.
Never collapse a workflow state into success
Store the Postdom post ID, read the exact destination state with get_publish, and preserve a missing public URL, approval state, terminal refusal, or provider error exactly as returned.
Nine modeled fields
Facebook Reels metric availability
The matrix records evidence states, not guaranteed live values. Unverified and never remain null with a reason; zero remains a measured zero.
viewsViewsRequired view count in a normalized snapshot.
2026-09-02T00:00:00.000Z
Numeric when a snapshot exists. Zero remains zero.
likesLikesRequired like count in a normalized snapshot.
2026-09-02T00:00:00.000Z
Numeric when a snapshot exists. Zero remains zero.
commentsCommentsRequired comment count in a normalized snapshot.
2026-09-02T00:00:00.000Z
Numeric when a snapshot exists. Zero remains zero.
sharesSharesRequired share count in a normalized snapshot.
2026-09-02T00:00:00.000Z
Numeric when a snapshot exists. Zero remains zero.
savesSavesNullable saved or favorited count.
Not verified
Always null with an explicit reason.
watch_time_sWatch timeNullable total watch time in seconds.
Not verified
Always null with an explicit reason.
avg_watch_pctAverage watchNullable average watched percentage.
Not verified
Always null with an explicit reason.
completion_pctCompletionNullable completion percentage.
Not verified
Always null with an explicit reason.
follower_deltaFollower deltaNullable follower-change field.
2026-09-02T00:00:00.000Z
Currently normalized to null; derivation is not promised.
Verification scope
Facebook Reels evidence boundary
Contract evidence is not an observed publication
These pages describe source-backed product contracts. They do not represent an authenticated end-to-end publication or analytics test.
Inspect the connected tool schema before acting. Current source may be ahead of the separately published @postdom/mcp helper.
Use the contract
Publish with explicit authority and outcomes
Create a workspace, connect an eligible account, and let the agent use only the fields exposed by the connected schema.