How to Debug WeChat Draft API Errors

"Why does the draft API keep failing?"

In most cases, the problem is not the endpoint itself. The problem is that the call sits in the middle of a longer chain. Content must be converted first. Images must stay usable. The cover image has its own constraints. Permissions often come from both the WeChat side and the service side. If any layer breaks, the final symptom looks the same: draft creation failed.

That is why debugging order matters more than throwing more logs at the issue.

Why the draft API fails more often than HTML conversion

A conversion endpoint only deals with rendering.
A draft endpoint deals with a publish-ready state.

That difference changes the failure surface:

• A conversion endpoint cares about Markdown, theme, font size, and layout
• A draft endpoint also cares about WeChat credentials
• It also cares about the cover image
• It often depends on whether article images survive the full workflow

The useful mental model is this:

A draft API is not a single feature. It is where content, media, and permissions meet.

If you want the higher-level context first, start here:

• What Is the WeChat Draft API, and Why Is It More Valuable Than HTML Conversion?
• Convert Markdown to WeChat HTML with md2wechat Agent API

The first class of errors: credentials do not line up

This is the most common problem, and it is also the one teams misread most often.

People tend to assume that if the service is reachable, draft creation should work. That assumption is wrong. A draft call usually depends on at least two permission layers:

• WeChat-side credentials such as appid and app secret
• Service-side credentials such as your API key

That gives you several common failure modes:

• The API key is valid, but the WeChat credentials are not
• The WeChat credentials work, but the service key is wrong for the current environment
• The headers look correct, but the values come from a different account or a different app

These failures often look random because the request itself still goes through. What changes is whether the downstream steps can continue.

The safer approach is to validate each layer separately:

1. Confirm that content conversion works on its own
2. Confirm that the WeChat credentials work on their own
3. Combine both layers only after the first two are stable

Do not start with the full request shape if you still do not trust the basics.

The second class of errors: the payload exists, but the content is not usable

Many draft failures do not come from a missing field. They come from content that looks complete but does not hold up in the rest of the workflow.

Typical examples:

• The Markdown is malformed
• An image URL is unstable or inaccessible
• The theme value is wrong
• The cover image field is present, but the asset is unusable
• The caller mixes Markdown and HTML assumptions in one request

The best response is simple:

Reduce the input to the smallest version that can succeed, then add complexity back one step at a time.

A good minimum payload usually means:

• Short Markdown
• One known-good theme
• One stable, reachable cover image
• No large code blocks
• No risky external images

If the smallest version works and the real article fails, you already know the bug is inside the article input, not the whole integration.

The third class of errors: article images and cover images get treated as one problem

They usually are not the same problem.

In many implementations, article images affect content completeness, while the cover image affects draft metadata. They may be validated differently and may move through different downstream steps.

Treat them separately.

For article images, verify these points

• The URL is reachable and stable
• The image format is valid
• The converted content still references the image correctly

For cover images, verify these points

• The field name is correct
• The asset URL remains available long enough for processing
• The draft flow actually accepts the current cover asset

If your product also exposes media-related capabilities, document this boundary clearly. Users are not asking whether "images are supported." They are asking whether the article can reliably land in the draft box.

For media-specific notes, continue with:

• WeChat Permanent Media Upload Guide

The fourth class of errors: the debugging order is backward

This happens all the time.

The bad order looks like this:

1. Start with the full draft API call
2. See a failure
3. Guess at the Markdown
4. Guess at the images
5. Discover much later that the credentials were wrong

The better order looks like this:

1. Prove that a small Markdown sample converts successfully
2. Confirm the theme and content structure
3. Confirm article images and cover assets separately
4. Attempt draft creation last

This order matters because each layer can be disproved independently. You stop mixing four classes of problems into one vague error.

If this runs inside an automated workflow, "success or failure" is not enough

Once draft creation runs inside scripts or workflow automation, the debugging model changes.

In that setup, a generic failure string is not enough. You need structured signals:

• A summary of the input it just sent
• Which stage failed: conversion, media, or draft creation
• Whether the error is retryable
• What the next action should be

Without that structure, retries and follow-up handling become fragile.

A practical debugging checklist

When draft creation fails again, check these six points in order:

1. Which WeChat credentials are active in the current environment
2. Whether the API key belongs to that same environment
3. Whether a minimal Markdown sample converts successfully
4. Whether the selected theme is known to be supported
5. Whether article images and cover images were validated separately
6. Whether the error response tells you which layer failed

There is nothing fancy in this list. It works because it strips the problem down to the real moving parts.

Closing thought

The draft API is not hard because the request body is long. It is hard because it sits at the intersection of permissions, content, and media.

Once you split failures into those layers, debugging gets much faster. If your goal is not an occasional article but a stable automated workflow, this split is not optional. It is the baseline.

For the broader workflow, continue with:

• How to Choose the Right Level of WeChat Automation
• What Makes a WeChat API Easier to Automate