Resolve a structured Apier compliance error code into a Norwegian-bokmål Explanation envelope sourced from the Apier Compliance Explainer (PR-049). The response carries a one-line summary, a 1–3 sentence why, an ordered list of fix_steps, an optional Apier / Altinn / Skatteetaten / Brønnøysund relevant documentation link, an optional Lovdata-style legal_basis citation when the error maps to a concrete regulatory provision, and an optional handover block (who / where / what / why) for errors a human must resolve (e.g. AUTH_INSUFFICIENT_ROLE, AUTH_NO_DELEGATION, SCOPE_MISSING). Errors agents can resolve themselves (VALIDATION_FAILED, RATE_LIMIT_EXCEEDED, NOT_FOUND, IDEMPOTENCY_KEY_MISMATCH, IDEMPOTENCY_IN_PROGRESS, UPSTREAM_UNAVAILABLE) ship `handover: null`. The full catalogue of supported error codes mirrors `EXPLAINER_ERROR_CODES` (40 codes today across auth, validation, scope, upstream, idempotency, action-execute, government, and reliability domains); pass any code an Apier endpoint returned in an error envelope. The optional `context` object carries placeholder values (org_number, role, scope, field, upstream_system) that the explainer interpolates into the bokmål text — missing values fall back to a Norwegian 'ukjent <noun>' rather than leaking placeholder syntax. Required scope: `read:rulebook`. For a company's live obligations rather than an error explanation, use get_company_obligations instead. No API key? Self-serve in the sandbox: authenticate tools/call with `Authorization: Bearer apier_sandbox_test_<suffix>` (ALWAYS append a unique random suffix, e.g. a fresh UUID, for session isolation) and this tool answers from deterministic synthetic fixtures with `_meta.is_sandbox: true` — use the reserved MOD-11-valid sandbox org numbers from GET /api/v1/sandbox/fixtures (e.g. 999660088).