Post with LangChain

Post to social media
with LangChain.

Wrap PostLake as one tool, or skip the wrapper and connect MCP. Either way the agent sees the same normalised Post response the Publishing docs describe.

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In shortOne LangChain tool (or MCP) that POSTs /v1/posts. Return the JSON so the agent can read targets[] and decide next steps.

When this guide is for you

You're building a LangChain agent that should post or schedule without registering nine social tools.

Before you start

Same setup the docs quickstart uses. Do this once:

Sign up at app.postlake.dev and verify your email (unlocks free credits).
On Channels, create a profile (e.g. my-brand) and connect at least one account. Bluesky is the fastest first channel: no app review. Instagram/TikTok/Facebook need each platform's review before API posting.
Account menu → API Keys → create a key (sk_live_…). It shows once; treat it like a password.

Working example in LangChain

Connect accounts once in the dashboard, then this is the publish call:

from langchain_core.tools import tool
import os, requests, uuid

@tool
def post_to_social(text: str, platforms: list[str] | None = None) -> dict:
    """Publish via PostLake. Returns the full Post object (check targets[])."""
    body = {"text": text, "profile": "my-brand"}
    if platforms:
        body["platforms"] = platforms  # filter only
    r = requests.post(
        "https://api.postlake.dev/v1/posts",
        headers={
            "Authorization": f"Bearer {os.environ['POSTLAKE_API_KEY']}",
            "Idempotency-Key": str(uuid.uuid4()),
        },
        json=body,
    )
    r.raise_for_status()
    return r.json()

# model.bind_tools([post_to_social]), or use MCP instead (no wrapper)

Make it work in LangChain

Tool-specific glue on top of the shared setup above:

Prefer MCP (https://api.postlake.dev/mcp) if your LangChain host supports it, OAuth. No key in the tool.
Otherwise define one tool that POSTs /v1/posts and returns the full JSON (not just "ok").
Instruct the agent to read state and each targets[].state before claiming success.
Always set Idempotency-Key (new UUID per logical post) so tool retries don't double-post.

Read the response (don't skip this)

You get one Post with an overall state and a targets[] array. One entry per account. Always check each target; partial success is normal.

{
  "id": "post_a1b2c3",
  "state": "partial",
  "targets": [
    { "platform": "bluesky",  "state": "published", "url": "https://bsky.app/…" },
    { "platform": "linkedin", "state": "failed",
      "error": { "type": "invalid_request", "message": "…", "retryable": false } }
  ]
}

published: every target succeeded. partial: some published, some failed. failed: none published. processing: still going (async networks like TikTok).
You're only charged for targets that actually publish. Failed targets cost nothing.
Send an Idempotency-Key header on writes so a retry never double-posts.
Full detail: Publishing · Errors & retries

Where the post goes

Same rules as the docs. Pick one addressing style:

By profile: "profile": "my-brand" posts to every account under that profile (the name on Channels).
Filter networks: "platforms": ["bluesky", "linkedin"] narrows that set. It is a filter, not a selector: if you have two Pinterest boards, both match pinterest.
By account id: "accounts": ["acc_…"] for exact channels (copy an id on Channels, or GET /v1/social-accounts).
One profile and you omit profile? PostLake uses that profile. Multiple profiles and you omit it? You'll get an error that names them.

See Publishing: where to post.

Do more (same API)

Schedule: add scheduledAt as UTC (trailing Z), or a naive local time plus timezone (IANA, e.g. Europe/London). Credits charge when it fires. Scheduling docs · scheduling guide.
Media: POST /v1/media, then pass the med_… id in media. Media docs.
Per-network caption: textOverrides (e.g. shorter text for X). Per-network options: platformOptions (Pinterest boardId, TikTok privacy, …). Live option lists: GET /v1/platforms/{platform}.
Validate first: POST /v1/posts/validate runs the same checks without publishing (free).

Pitfalls specific to this path

If the tool returns only a string "posted", the agent cannot handle partial failure, return the Post object.
Don't give the agent a separate tool per network; one PostLake tool is enough.
Validate long drafts with POST /v1/posts/validate (or the MCP validate tool) before publish.

Want zero wrapper code? Connect the hosted MCP server (https://api.postlake.dev/mcp) over OAuth. Same accounts and responses as this API path. Agents overview.

Common questions

How do I let a LangChain agent post to social media?

Either connect PostLake MCP, or bind one tool that POSTs /v1/posts with text + profile and returns the JSON. The agent then handles every connected network through that one tool.

Do I need a tool per social network?

No. One tool calling PostLake covers the profile. Use platforms only as an optional filter.

Can LangChain use PostLake over MCP?

Yes. Point the host at https://api.postlake.dev/mcp and complete OAuth. Tools for publish, schedule, validate, and analytics appear without a custom wrapper.

Go deeper in the docs

These guides stay short on purpose. Canonical behaviour lives here:

Also: Media · Errors · MCP · Analytics

Stuck? The docs are the source of truth, start at Publishing.

Open the dashboard →

Post to social mediawith LangChain.

When this guide is for you

Before you start

Working example in LangChain

Make it work in LangChain

Read the response (don't skip this)

Where the post goes

Do more (same API)

Pitfalls specific to this path

Common questions

Go deeper in the docs

Quickstart

Publishing

Scheduling

Platforms

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Post to social media
with LangChain.