Anthropic

Add an Anthropic API key so MagicPost can write captions, post versions and alt text with Claude models.

Anthropic provides writing models in MagicPost: captions, versions of one post adapted for several networks, and alt text for pictures. Anthropic has no picture or video models here. Use OpenAI, Google Gemini, xAI Grok or fal.ai for those.

The key is entered on Writing Models only. Media Models has no Anthropic section.

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Before you start

• You can sign in to the MagicPost admin panel.
• You have an Anthropic account with API billing or credits set up. Anthropic bills you directly for every request. This is separate from the credits your users spend in MagicPost.

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Get an API key

1. Sign in to the Claude Console

   Go to platform.claude.com and sign in or create an account.

2. Add credits or billing

   Open the billing settings and add a payment method or credits so requests can go through.

3. Create the key

   Go to Settings → API keys and click Create key. Name it (for example, MagicPost). You can also pick a workspace for the key and set an expiry. If you set an expiry, plan to replace the key before that date.

   The console shows the full key only once. Copy it now. If you lose it, create a new key.

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Add the key in MagicPost

1. Open Writing Models

   Go to Admin → Publishing → Writing Models.

2. Paste the key

   In the Provider keys box, paste the key into the Anthropic Claude field and click Save keys. The toast reads Keys saved. and the Anthropic Claude card shows Key stored.

3. Switch on the models

   Turn on the switch next to each Claude model you want to offer, then click Test on one of them. MagicPost sends a one-word request and shows either that the model answered or the error Anthropic returned.

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Starting models

The installer loads this list. Identifiers are as shipped and can be corrected later (see Model identifiers). Credits are MagicPost credits, not Anthropic prices, and you can change them on the model.

Model	Identifier	Tier	Starting credits per run
Claude Opus 4.8	claude-opus-4-8	Premium	4
Claude Sonnet 4.6	claude-sonnet-4-6	Standard	2
Claude Haiku 4.5	claude-haiku-4-5	Fast	1

For every field you can edit on a model, see AI models.

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How MagicPost calls Anthropic

• Requests go to Anthropic’s Messages API with your key in the x-api-key header. MagicPost also sends the API version header that Anthropic requires, so you do not configure it.
• Opus 4.7 and later Opus versions, and every model from generation 5 on, refuse any temperature except their default. MagicPost sends no temperature to them. If another model rejects temperature by name, MagicPost sends the request again without it and remembers that for the model.
• Pictures attached to a caption request are sent along with the question. Claude 3 and later models are treated as able to look at pictures.

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Troubleshooting

Symptom	Likely cause	Fix
Keys saved. but the card still reads No key	The Anthropic Claude field was empty when you saved	Paste the key and click Save keys again
Test says to add the Anthropic Claude API key first	No key is stored	Paste the key on Writing Models and save
Test fails with an authentication or permission message from Anthropic	The key is wrong, revoked, expired, or its workspace cannot use the model	Create a new key and save it
Test fails with a not found or unknown model message	Anthropic no longer has that identifier	Click Edit and correct Model identifier
The model returned nothing. Try again, or pick a different model.	The reply had no text	Try again or switch to another model
Users see that no writing model is available	No model has both a stored key and its switch on	Store a key and switch at least one model on
Keys stopped working after moving the site	APP_KEY changed, so the stored key cannot be decrypted	Paste the key again and click Save keys