accounted/extensions/general/mcp-server

Accounted MCP server

JSON-RPC 2.0 server exposing the Accounted bookkeeping engine to MCP clients (Claude Desktop, Claude Code, etc.). Endpoint: /api/extensions/ext/mcp-server/mcp. Add ?tool_namespace=accounted for the Accounted tool names. Requests without it retain the legacy Gnubok namespace. OAuth and stdio bridges live alongside the API surface: see app/api/mcp-oauth/, packages/accounted-mcp/, and the compatibility package in packages/gnubok-mcp/.

Tool authoring contract

Enforced by tests in __tests__/: these are not style preferences, they're guard rails.

1. additionalProperties: false on every inputSchema. Guarded by strict-schemas.test.ts. Forces clear rejections on hallucinated fields instead of silent ignores.
2. Descriptions ≤ 280 chars. Guarded by output-schema.test.ts. No Args: / Returns: / Examples: prose: those belong in JSON Schema. Use agent-native hints ("Use to…", "Call X first", "HIGH risk").
3. Staged-operation envelope for write tools: outputSchema: STAGED_OPERATION_SCHEMA (server.ts). Fields: staged, risk_level, actor, message, preview, period_status?, next?. The staged: true boolean is the explicit completion signal; agents must not infer completion from prose. Do NOT introduce a parallel { success, shouldContinue, output } envelope.
4. period_status threading: any tool that ties to a fiscal-period-bound date (categorize, mark paid, create voucher, correct/reverse entry, approve supplier invoice) passes dateForPeriodCheck to stagePendingOperation. Response then includes period_status: { period_id, status: open|locked|closed, lock_date } so widgets and agents disable writes without round-trips.
5. Scope mapping: every new tool needs an entry in lib/auth/api-keys.ts TOOL_SCOPE_MAP. Missing entries default to deny.
6. Tests for new write tools: add staging-gate coverage to __tests__/voucher-tools.test.ts (or a sibling) plus executor coverage to lib/pending-operations/__tests__/voucher-executors.test.ts if the tool stages a new operation_type.

Determinism / cache stability

Tool definitions (name, description, inputSchema, outputSchema, annotations) are declared as static object literals at module load: no timestamps, no UUIDs, no Date/Math.random in the definition layer. This makes the tools/list JSON payload byte-stable across requests, which lets agent-side prompt caches stay warm. Do not introduce per-request non-determinism into the definitions block. Anything time-bound or random belongs inside execute().

For internal Anthropic API usage (the SDK is called from lib/ai/provider.ts and lib/ai/services/anthropic-family.ts; features such as extensions/general/invoice-inbox/lib/extract-invoice-fields.ts go through getAiService() in lib/ai rather than the SDK directly): annotate stable prefixes with cache_control: { type: 'ephemeral' } and log usage.cache_read_input_tokens for hit-ratio observability. The 1h TTL from the agent-native API plan (item 10) requires the direct Anthropic API; Accounted's Bedrock path defaults to a shorter TTL.

Payload-size watchdog

payload-size.bench.test.ts enforces a tools/list JSON payload ceiling. If the test fires, the right answer is rarely "raise the ceiling". Instead, trim descriptions or set specialized wide tools to catalogVisibility: 'search'. Those tools remain discoverable with full schemas through gnubok_search_tools and callable through tools/call without bloating the default catalog.

Where things live

• server.ts: the tools array + JSON-RPC dispatcher
• tool-result.ts: withNext(), toToolError() response helpers
• resources/: read-only Accounted:// URIs, registered in resources/index.ts: company/current, period/active, recent-activity, capabilities, attention, chart-of-accounts, settings/vat-treatments, booking-templates, ledger/context, reconciliation/summary
• widgets/: inline HTML widgets (receipt-matcher, vat-review, pending-operations)
• prompts/: slash-command-style prompts
• skills/: domain-knowledge skill bodies served via gnubok_load_skill
• public-tools.ts: lazy authentication (issue #1814). ANONYMOUS_METHODS (initialize, ping, tools/prompts/resources listing) and the three PUBLIC_TOOLS (gnubok_search_tools, gnubok_list_skills, gnubok_load_skill) answer without credentials, rate-limited per truncated IP; every other tools/call gets a transport-level 401 + WWW-Authenticate from handleMcpRequest in server.ts, which is the challenge clients turn into their Connect prompt
• tasks.ts: MCP Tasks extension (io.modelcontextprotocol/tasks): durable handles for long-running tool calls, rows in mcp_tasks (service-role writes only)
• origin-guard.ts: Origin-header validation on the Streamable HTTP endpoint (DNS-rebinding defence required by the MCP spec)
• staging-pii-guard.ts: refuses a plaintext personnummer in staged pending_operations params/preview, so every staging tool inherits the encrypt-at-staging rule
• tool-namespace.ts: ?tool_namespace=accounted handling (accounted_* aliases for the canonical gnubok_* ids)
• __tests__/: strictness guards + per-tool coverage