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alt-text-writer

Skill2 starsChanged 23 days agoMITView on GitHub

Write accurate alt text and a figure caption for any image file — a vision model looks at the actual pixels and returns JSON with a 125-char alt string and a one-sentence caption. Use when filling in alt="" attributes, writing figure captions, or describing screenshots the agent cannot see.

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The file

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1 rule. About 0 are common, 1 is distinctive, and 0 are very specific to this project.

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  1. Distinctive:

    Never print the key.

    line 27

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Files
SKILL.md

Alt-text writer

Runs the bundled nanoodle workflow workflows/alt-text.noodle-graph.json against the NanoGPT API: an image input (Image) feeds a vision model whose question is assembled from two text nodes — the alt-text rules (Alt rules) and an optional house style guide (Style guide) — and the output (Alt text) is JSON with alt_125char and numbered_caption. Requires Node.js 22.23.4+, 24.22.1+, or 26.12.1+ and the nanoodle npm package (npx nanoodle fetches it).

Typical agent use: mid-PR, glob the repo's images, call this once per file, and write the returned alt_125char into the markup instead of guessing at pixels you cannot see.

API key

The run needs a NanoGPT API key. Use whichever is available:

  • NANOGPT_API_KEY already set in the environment — prefer this; no extra flags.
  • A .env file containing NANOGPT_API_KEY=... — pass --env-file <path> only when the key is not already in the environment. (With this CLI, --env-file overrides ambient NANOGPT_API_KEY.)

Never print the key.

Run

From this skill's directory (or prefix paths if running from elsewhere). Replace the image path with the real file (@path attaches a local file; an https:// URL also works):

npx nanoodle run workflows/alt-text.noodle-graph.json \
  --input "Image=@/path/to/image.jpg"

The output is text, so no --out directory is needed. For a machine-readable payload (outputs, cost, balance), the run summary JSON is always printed on stdout.

Optional overrides (both have baked-in defaults):

--input "Alt rules=<different output instructions>"
--input "Style guide=@docs/style-guide.md"

Inspect the interface anytime with:

npx nanoodle inspect workflows/alt-text.noodle-graph.json

Inputs

KeyRequiredWhat to pass
ImageyesImage file path (@path) or https URL
Alt rulesno (default baked in)Alternative instructions for the metadata format
Style guideno (default baked in)House wording rules to apply

Outputs

  • Alt text is a text output: the CLI prints it on the Alt text: stderr line and includes it in the stdout JSON as outputs["Alt text"] — a JSON string with alt_125char and numbered_caption keys. Parse it from stdout.

Serve as an MCP tool

The same graph file works unchanged as a typed MCP tool — copy it into the folder nanoodle-mcp serves and the agent gets an alt-text tool with Image required:

mkdir -p ~/noodles && cp workflows/alt-text.noodle-graph.json ~/noodles/alt-text.json
claude mcp add nanoodle -- npx nanoodle-mcp --graphs ~/noodles

Cost

Each run costs a fraction of a cent (one gemini-2.5-flash-lite vision call). Cheap enough to fan out over a whole docs folder, but each call still spends real NanoGPT credit — the CLI prints the metered cost after every run.

Download now (ZIP)

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