Still very interested in this as well

Attempting to build out some personal automation to cover the gap, found that API documentation is on any misskey server using /api-doc

https://misskey.io/api-doc is available for example, but sign ups are limited to Japan for that server

I have a misskey-fork server i would be willing to volunteer for testing. (Running Sharkey)

Or would be willing to volunteer spinning up a temporary vanilla misskey server if it would help testing/development!

Following the API doc with some AI help I was able to get the following bash script made that works for posting, not sure if this would help cut dev time

#!/bin/bash

# Variables
MISSKEY_SERVER="example.com"
MISSKEY_API_TOKEN="YOUR_API_TOKEN_HERE"
POST_TEXT="YOUR TEXT HERE"
IMAGE_URL="https://static.vecteezy.com/system/resources/previews/004/349/996/non_2x/television-screen-error-tv-test-pattern-and-tv-no-signal-concept-smpte-color-bars-illustration-free-vector.jpg"  # Leave empty "" if no image
DEFEDERATE=true  # true or false
DEBUG=false       # Enable debug output

# Headers common to all requests
AUTH_HEADER="Authorization: Bearer $MISSKEY_API_TOKEN"
CONTENT_TYPE_HEADER="Content-Type: application/json"

# Function to upload image from URL
upload_image() {
  curl -s -X POST "https://$MISSKEY_SERVER/api/drive/files/upload-from-url" \
    -H "$AUTH_HEADER" -H "$CONTENT_TYPE_HEADER" \
    -d "{\"url\":\"$IMAGE_URL\",\"isSensitive\":false,\"force\":true}"
}

# Function to find uploaded image info by filename
find_image() {
  filename=$(basename "$IMAGE_URL")
  curl -s -X POST "https://$MISSKEY_SERVER/api/drive/files/find" \
    -H "$AUTH_HEADER" -H "$CONTENT_TYPE_HEADER" \
    -d "{\"name\":\"$filename\",\"limit\":1}"
}

# Function to post a note without image
post_note_no_image() {
  curl -s -X POST "https://$MISSKEY_SERVER/api/notes/create" \
    -H "$AUTH_HEADER" -H "$CONTENT_TYPE_HEADER" \
    -d "{\"text\":\"$POST_TEXT\",\"visibility\":\"public\",\"localOnly\":$DEFEDERATE}"
}

# Function to post a note with image file ID(s)
post_note_with_image() {
  file_id="$1"
  curl -s -X POST "https://$MISSKEY_SERVER/api/notes/create" \
    -H "$AUTH_HEADER" -H "$CONTENT_TYPE_HEADER" \
    -d "{\"text\":\"$POST_TEXT\",\"visibility\":\"public\",\"localOnly\":$DEFEDERATE,\"fileIds\":[\"$file_id\"]}"
}

# Main logic
if [[ -z "$IMAGE_URL" ]]; then
  if $DEBUG; then
    echo "[DEBUG] No IMAGE_URL specified. Posting text only."
  fi
  post_note_no_image
else
  if $DEBUG; then
    echo "[DEBUG] Uploading image..."
  fi
  upload_response=$(upload_image)
  if $DEBUG; then
    echo "[DEBUG] Upload response (Expected to be Empty): $upload_response"
  fi

  # Wait a few seconds to allow the server to process the uploaded file
  sleep 5

  if $DEBUG; then
    echo "[DEBUG] Searching for uploaded image by filename..."
  fi
  find_response=$(find_image)
  if $DEBUG; then
    echo "[DEBUG] Find response: $find_response"
  fi

  # Extract file ID from find response (array, first element)
  file_id=$(echo "$find_response" | jq -r '.[0].id')

  if [[ -z "$file_id" || "$file_id" == "null" ]]; then
    echo "[ERROR] Failed to get valid file ID from find response."
    exit 1
  fi

  if $DEBUG; then
    echo "[DEBUG] Extracted file ID: $file_id"
    echo "[DEBUG] Posting note with image..."
  fi

  post_response=$(post_note_with_image "$file_id")
  if $DEBUG; then
    echo "[DEBUG] Post note response: $post_response"
  fi
fi

Adding to this that I would also be happy to provide a testing instance for these as well! I run a sandbox instance for testing all kinds of things! https://sandbox.baka.social/