Function fetchCapabilities

fetchCapabilities(
    config: B2Config,
    capabilityCacheKey?: string,
    logKey?: string,
): Promise<string[] | null>
Discover the B2 key capabilities used for capability-aware registration.
Parameters
- config: B2Config
  B2 credential and runtime configuration.
- OptionalcapabilityCacheKey: string
  Optional cache key override for tests or caller-specific HTTP routing.
- OptionallogKey: string
  Optional non-secret log key override.
Returns Promise<string[] | null>
A copy of the discovered capabilities, or null when registration should expose the full tool surface.
Remarks
The returned capabilities come from b2_authorize_account and decide which tools are even registered for the credential. Setting B2_REGISTER_ALL_TOOLS=true is the explicit operator/test escape hatch and returns null; all other authorization failures are sanitized and thrown so internet-facing servers fail closed.

Positive non-empty results are cached briefly by credential fingerprint and concurrent discoveries for the same key share one in-flight authorize call.

Throws
CredentialResolutionError when B2 authorization or capability discovery fails.
Example
```
const capabilities = await fetchCapabilities(config);
const server = createServer(config, capabilities);
```
- Defined in server.ts:745