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feat: support images in custom tool responses #9539
Description
Problem
Custom tools (defined in .opencode/tools/) can currently only return strings. MCP tools already support returning structured content with images via { content: [{type: "image", mimeType, data}] }. This limitation prevents custom tools from returning visual data like screenshots, charts, or processed images that the LLM could analyze.
Proposed Solution
Extend the custom tool API to support the same rich content pattern as MCP tools:
export default tool({
description: 'Capture a screenshot',
args: { url: z.string() },
async execute(args) {
const base64 = await captureScreenshot(args.url)
return {
content: [
{ type: 'text', text: 'Screenshot captured' },
{ type: 'image', mimeType: 'image/png', data: base64 }
]
}
}
})Requirements
- Custom tools can return either
string(backwards compatible) or{ content: ToolContentPart[] } - Images are converted to attachments and sent to the model (same as MCP tools)
- Existing string-only tools continue to work unchanged
- Validation for image mime types and size limits
Related
- PR feat: support images in mcp tool responses #4100 added image support for MCP tools - this extends that pattern to custom tools
Reacted by leeweisern
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github-actions commentedon Jan 20, 2026
This issue might be a duplicate of existing issues. Please check:
tool.execute.afteroutput has two different formats #2897: Tool.execute.after output has two different formats - related to standardizing structured responsestool.execute.afterhook to modify MCP tool output #3384: Allow tool.execute.after hook to modify MCP tool output - related to output handling consistencyFeel free to ignore if none of these address your specific case.
feat(plugin): support images in custom tool responses
leeweisern commentedon Jan 20, 2026
Currenty i am turning my custom tools into mcp to support images....
guilhermelowa commentedon Jan 20, 2026
It would be super helpful to have this tool!
Samraaj commentedon Feb 27, 2026
+1 i need dis
github-actions commentedon Apr 29, 2026
To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.