Cross-post formatter API

Paste one post and see at once where it fits on X, Threads, Bluesky, Mastodon and LinkedIn. Each network counts with its own rules, and you get a ready thread wherever the post is too long.

• Endpoint: POST https://postboost.co/app/api/tools/cross-post-formatter (operationId formatCrossPost)
• Web tool: postboost.co/tools/cross-post-formatter
• Token: optional (limits)
• MCP: tool format-cross-post on https://postboost.co/mcp/tools

Request

Field	Type	Default	Description
text	string	""	The post text, up to 10,000 characters.
networks	array of string	["x","threads","bluesky","mastodon","linkedin"]	The networks to format for, in the order the result lists them.
numbering	boolean	false	End each post of a thread with " k/n".

Call it

curl

curl -X POST https://postboost.co/app/api/tools/cross-post-formatter \
  -H 'Content-Type: application/json' \
  -d '{"text":"Our spring menu is live, thanks @alice for the photos: https://example.com/menu","networks":["x","mastodon","linkedin"]}'

Python

from postboost import ApiClient, Configuration
from postboost.api.free_tools_api import FreeToolsApi
from postboost.models import FreeToolFormatCrossPostRequest

with ApiClient(Configuration()) as client:
    api = FreeToolsApi(client)
    result = api.format_cross_post(FreeToolFormatCrossPostRequest.from_dict({"text": "Our spring menu is live, thanks @alice for the photos: https://example.com/menu", "networks": ["x", "mastodon", "linkedin"]}))
    print(result.to_dict())

Node.js

import { FreeToolsApi } from 'postboost';

const api = new FreeToolsApi();
const { body } = await api.formatCrossPost({ text: "Our spring menu is live, thanks @alice for the photos: https://example.com/menu", networks: ["x", "mastodon", "linkedin"] });
console.log(body);

PHP

use PostBoostClient\Api\FreeToolsApi;
use PostBoostClient\Model\FreeToolFormatCrossPostRequest;

$api = new FreeToolsApi(new GuzzleHttp\Client());
$result = $api->formatCrossPost(new FreeToolFormatCrossPostRequest(['text' => "Our spring menu is live, thanks @alice for the photos: https://example.com/menu", 'networks' => ["x", "mastodon", "linkedin"]]));
echo $result;

Go

import (
    "context"
    "encoding/json"
    "fmt"

    postboost "github.com/postboost-co/postboost-go"
)

var request postboost.FreeToolFormatCrossPostRequest
if err := json.Unmarshal([]byte(`{"text":"Our spring menu is live, thanks @alice for the photos: https://example.com/menu","networks":["x","mastodon","linkedin"]}`), &request); err != nil {
    panic(err)
}

client := postboost.NewAPIClient(postboost.NewConfiguration())
result, _, err := client.FreeToolsAPI.FormatCrossPost(context.Background()).FreeToolFormatCrossPostRequest(request).Execute()
fmt.Println(result, err)

Ruby

require 'postboost'

api = PostBoost::FreeToolsApi.new
result = api.format_cross_post(PostBoost::FreeToolFormatCrossPostRequest.new({ text: "Our spring menu is live, thanks @alice for the photos: https://example.com/menu", networks: ["x", "mastodon", "linkedin"] }))
puts result.to_hash

Java

import com.postboost.ApiClient;
import com.postboost.api.FreeToolsApi;
import com.postboost.model.FreeToolFormatCrossPostRequest;
import com.postboost.model.FreeToolFormatCrossPostResponse;

FreeToolsApi api = new FreeToolsApi(new ApiClient());
FreeToolFormatCrossPostRequest request = FreeToolFormatCrossPostRequest.fromJson("{\"text\":\"Our spring menu is live, thanks @alice for the photos: https://example.com/menu\",\"networks\":[\"x\",\"mastodon\",\"linkedin\"]}");
FreeToolFormatCrossPostResponse result = api.formatCrossPost(request);
System.out.println(result.toJson());

C#

using Newtonsoft.Json;
using PostBoost.Client.Api;
using PostBoost.Client.Client;
using PostBoost.Client.Model;

var api = new FreeToolsApi(new Configuration());
var request = JsonConvert.DeserializeObject<FreeToolFormatCrossPostRequest>(@"{""text"":""Our spring menu is live, thanks @alice for the photos: https://example.com/menu"",""networks"":[""x"",""mastodon"",""linkedin""]}");
var result = await api.FormatCrossPostAsync(request);
Console.WriteLine(result.ToJson());

Rust

use postboost::apis::configuration::Configuration;
use postboost::apis::free_tools_api;
use postboost::models::FreeToolFormatCrossPostRequest;

let config = Configuration::new();
let request: FreeToolFormatCrossPostRequest = serde_json::from_str(r##"{"text":"Our spring menu is live, thanks @alice for the photos: https://example.com/menu","networks":["x","mastodon","linkedin"]}"##)?;
let result = free_tools_api::format_cross_post(&config, request).await?;
println!("{:?}", result);

CLI

echo '{"text":"Our spring menu is live, thanks @alice for the photos: https://example.com/menu","networks":["x","mastodon","linkedin"]}' | ./postboost-cli --content-type application/json formatCrossPost -

With a token, send Authorization: Bearer YOUR_API_TOKEN as a default header (how, per SDK).

Response

{
    "networks": [
        {
            "key": "x",
            "label": "X (Twitter) post",
            "limit": 280,
            "count": 78,
            "fits": true,
            "over_by": 0,
            "links": 1,
            "warnings": [
                {
                    "code": "mentions_not_portable",
                    "message": "@handles are per network: check each one exists on X (Twitter)."
                }
            ],
            "thread": null
        },
        {
            "key": "mastodon",
            "label": "Mastodon post",
            "limit": 500,
            "count": 78,
            "fits": true,
            "over_by": 0,
            "links": 1,
            "warnings": [
                {
                    "code": "mentions_not_portable",
                    "message": "@handles are per network: check each one exists on Mastodon. Use @user@server for people on other servers."
                }
            ],
            "thread": null
        },
        {
            "key": "linkedin",
            "label": "LinkedIn post",
            "limit": 3000,
            "count": 79,
            "fits": true,
            "over_by": 0,
            "links": 1,
            "warnings": [
                {
                    "code": "mentions_not_portable",
                    "message": "@handles are per network: check each one exists on LinkedIn."
                }
            ],
            "thread": null
        }
    ]
}

With MCP

Connect https://postboost.co/mcp/tools (setup) and ask, for example: Format one post for X, Threads, Bluesky, Mastodon and LinkedIn with the PostBoost format-cross-post tool.

Errors

Status	When
401	The Authorization header holds an invalid token. Leave it out to call as a guest.
413	The JSON body is larger than 128 KB.
422	A field is invalid; the body lists the errors per field.
429	A limit is reached; see limits.