Expose configured Huabu capabilities to external agents

[mydmdm]

Summary

Expose Huabu capabilities to external agents through a secure, capability-scoped interface. External agents should be able to use the same user-configured Huabu capabilities that are available to the native experience, without receiving raw credentials or bypassing Huabu authorization and policy controls.

Motivating examples

• Web search: allow an external agent to invoke web search using the user's configured Tavily token and Huabu's existing search behavior.
• Image generation: allow an external agent to request image generation using the user's configured model/provider and Huabu's existing image-generation flow.
• Future capabilities: make it possible to add more Huabu tools—such as document/file operations, media processing, or other model providers—without creating a separate integration for every external agent runtime.

Requirements

• Define a stable external-agent capability contract and tool discovery mechanism.
• Expose capabilities by explicit allowlist and scope, not by granting unrestricted access to Huabu internals.
• Keep provider credentials, tokens, model configuration, and other secrets server-side; external agents receive operation results, not raw secrets.
• Reuse the user's existing Huabu configuration, authorization, quotas, policy checks, and audit/error semantics.
• Support capability-specific input validation, cancellation/timeouts, bounded resource use, and clear errors when a capability is unavailable or not configured.
• Preserve Space, Canvas, tenant, and user authorization boundaries for every invocation.
• Make the interface usable by external agent runtimes over the supported agent/RFS integration surface, with documentation and examples.
• Define compatibility/versioning expectations so capabilities can evolve without silently changing behavior for existing agents.

Security considerations

• Never inject Tavily tokens, model-provider credentials, or other secrets into agent prompts, tool descriptions, generated HTML, or client-visible state.
• Prevent an external agent from selecting arbitrary credentials, providers, models, or scopes outside the user's authorized configuration.
• Apply rate limits, cost controls, origin/thread attribution, and audit logging consistently with native Huabu operations.
• Return only the minimum result data required by the requested capability.

Acceptance criteria

• An external agent can discover whether web search and image generation are available.
• An authorized external agent can invoke web search using the user's configured Tavily integration without seeing the token.
• An authorized external agent can invoke image generation using the user's configured model/provider without seeing provider credentials.
• Unauthorized, unconfigured, invalid, timed-out, and over-limit requests fail explicitly and safely.
• Existing native Huabu capability behavior remains compatible.
• The capability contract, authorization model, credential boundary, lifecycle, and at least one integration test per initial capability are documented.