Accessibility Describe
A RocketRide image node that converts an image into a safety-oriented scene description for blind and visually impaired users. Choose it when the next step needs accessible text, including hazards, spatial references, visible text, and navigation guidance.
About Google Gemini
Google Gemini is the vision-model provider used by this node through the
google-genai Python package. The node sends image bytes and its analysis
prompt to the configured Gemini model in one content-generation request.
What it does
The node buffers an incoming image stream until it finishes, then passes the
image and configured analysis prompt to Gemini and writes Gemini's response to
the text lane. Its built-in instructions emphasize hazards, spatial
orientation, readable text, concision, and environmental context; the default
analysis prompt requests environment, hazards, objects, text, people, and
navigation in fewer than 150 words.
It is a pipeline filter, not an agent tool. Use it for a complete accessibility-focused narration instead of an image operation whose downstream consumer needs another kind of result. An empty image stream produces no text.
Lanes
| Lane in | Lane out | Description |
|---|---|---|
image | text | Analyze the completed image stream and emit the generated description. |
Profiles
Default: Gemini 2.5 Flash - Fast & Efficient (1M tokens) (gemini-2.5-flash).
| Profile | Model | Context limit |
|---|---|---|
| Gemini 2.5 Flash - Fast & Efficient (1M tokens) (default) | gemini-2.5-flash | 1048576 tokens |
| Gemini 2.5 Pro - High Quality (1M tokens) | gemini-2.5-pro | 1048576 tokens |
| Gemini 2.0 Flash - Balanced (1M tokens) | gemini-2.0-flash | 1048576 tokens |
Configuration
Start with the default Flash profile, provide its API key, and keep the built-in instructions and prompt if their safety-first structure fits the task. Adjust the text fields when the user needs a different description policy, then use the two formatting controls to make the output easier to act on. The model and context-limit values are supplied by the selected profile.
System Instructions
This text is the model's system instruction. By default it directs the model to lead with hazards, use clock positions and relative distances, read visible text exactly, favor actionable information, and identify the environment and landmarks. Change it for a durable policy that should apply to every image—for example, to add a site-specific safety rule—rather than to ask about one image.
An empty value falls back first to the generic systemPrompt runtime setting,
then to the built-in instruction. The selected hazard priority and spatial
format are appended to this instruction, so keep it compatible with those
controls instead of duplicating contradictory spatial or ordering rules.
Analysis Prompt
The analysis prompt is the per-image request. Its default requests six sections—environment, hazards, key objects, text, people, and navigation—and asks Gemini to keep the description under 150 words. Change it when the output has to match a particular consumer or structure; for example, ask for a brief navigation-only description when a downstream voice interface must respond quickly.
Leaving it empty falls back to the generic prompt runtime setting and then to
the built-in prompt. The implementation sends this text with the image, while
the system instructions remain a separate model setting.
Hazard Priority
This control appends a safety-ordering instruction to the system prompt. The
default high tells the model to lead with hazards and to state that the area
appears safe when it finds none. Choose medium to include hazards in their
spatial context without requiring them first, or low for no extra hazard
emphasis. Keep high for navigation-oriented descriptions; lower it only when
another description order is more useful.
Spatial Format
This control appends the requested spatial-language style to the system prompt.
clock, the default, asks for clock positions with 12 o'clock straight ahead;
relative asks for left, right, ahead, and behind; both asks for both forms.
Use relative for readers unfamiliar with clock positions, or both when
redundant orientation is valuable. It works alongside Hazard Priority because
hazards can use whichever spatial convention is selected.
Authentication
Set the selected profile's Google AI API key in the node configuration. The
node will not start without a key, and it rejects a value beginning with sk-
as an OpenAI key rather than sending it to Gemini. Create the required key in
Google AI Studio.
Notes
Request and failure behavior
At the end of the image stream, the node base64-encodes the received bytes into
a data URL and sends the decoded bytes to Gemini with temperature 0.3 and a
maximum of 1024 output tokens. It makes one initial request plus up to three
retries for errors whose messages indicate a timeout, connection failure, HTTP
500, 502, 503, or 504, or an internal server error; retry waits are 1,
2, and 4 seconds.
If all attempts fail, it raises an accessibility-vision error. Authentication, rate-limit, invalid-input, unavailable-model, timeout, and safety-block messages are translated to user-facing error text; other failures retain the Google AI error message. A missing image or malformed image data URL raises a value error before the model request.
Upstream docs
Schema
| Field | Type | Description | Default |
|---|---|---|---|
accessibility.prioritizeHazards | string | Hazard Priority How aggressively to prioritize hazard detection | "high" |
accessibility.prompt | string | Analysis Prompt Prompt template for generating accessibility descriptions from images | "Describe this image for a blind person. Include: environment type, hazards with positions, key objects with clock positions, visible text, people, and navigation guidance. Keep under 150 words." |
accessibility.spatialFormat | string | Spatial Format How to describe spatial positions | "clock" |
accessibility.systemPrompt | string | System Instructions Define the accessibility description behavior and priorities | "You are an accessibility-focused scene analyzer designed to help blind and visually impaired users understand their surroundings through image descriptions." |
accessibility_describe.profile | string | Vision Model Select the Gemini vision model for accessibility descriptions | "gemini-2.5-flash" |
model | string | Model Google Gemini vision model | |
modelTotalTokens | number | Tokens Maximum context length in tokens |
Dependencies
google-genai>=1.14.0