Agent skill dependency injection: allow skills to declare required env vars

[leocagli]

Context

Skills registered in the marketplace may need API keys or config values (e.g. an LLM skill needs OPENAI_API_KEY). Currently there's no way to declare or validate these at registration time — missing config is only discovered at invocation.

What to implement

Registration: requiredEnv field

POST /api/skills/register accepts optional requiredEnv: string[] — an array of env var names the skill needs.

Validation at registration

Server checks process.env[key] !== undefined for each entry. If any are missing, return:

{ "ok": false, "error": "missing_env", "missing": ["OPENAI_API_KEY"] }

Listing: surface missing deps

GET /api/skills includes { requiredEnv: string[], envSatisfied: boolean } per skill. Agents can filter for only skills with envSatisfied: true.

Acceptance criteria

• Registering with a missing env var returns 400 with the missing key name
• Registering with all env vars present succeeds
• GET /api/skills shows envSatisfied: false when a var was present at registration but removed later
• Invoking a skill with envSatisfied: false returns 503 with error: "skill_config_unavailable"
• Unit tests: missing env on register, runtime var removal, satisfied flow

[Glam26]

I've implemented similar configuration validation and runtime dependency checks before, ensuring services fail fast when required environment variables are missing while providing clear, actionable error messages. I'm experienced with designing APIs that expose configuration health and keeping registration and runtime validation consistent.

For this task, I'll extend the skill registration API with requiredEnv validation, expose requiredEnv and envSatisfied in the skills listing, enforce runtime availability checks before invocation, and add comprehensive unit tests covering missing environment variables, runtime configuration changes, and the successful execution path.

[grantfox-oss]

🦊 GrantFox — @Glam26 has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #318)
2. Your PR will be reviewed by the Bitcoindefi maintainers

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