v0.3.0

Added

• defineTool(...) — FastMCP-style typed tools: input is inferred from inputSchema and a
  mutating tool's execute(data) is typed from preview's data, so handlers need no casts.
• Handlers and execute may return a plain string (→ one text block) or any JSON-serializable
  value (→ JSON text block); an MCP { content: [...] } result still passes through unchanged.
• ToolError — throw it from a handler, preview, or execute to reject with a message the
  client sees verbatim (e.g. "09:00 is already booked"). Any other error stays generic.
• onToolError hook, fired when a handler/preview/execute throws or returns an
  unserializable value, or a storage call in the mutating flow fails (phase: "storage") —
  the real error is no longer invisible to the operator. A storage failure before
  execute releases the idempotency claim so a retry can run.
• onToolCall now also fires for mutating-tool calls (the preview step).
• name / version config options for the server identity reported on initialize.

Changed

• Breaking: createMcpServer now throws at construction on duplicate tool names, a tool
  named confirm_request (reserved), a tool scope not declared in scopes, or an
  inputSchema that isn't a z.object. That includes object schemas wrapped in
  .transform() / .pipe() / .default() / .readonly(), and — under zod 3 — .refine() /
  .superRefine() / .brand(). Such tools previously started but were advertised with an
  empty input schema and received unvalidated input; move that logic into the handler.
• Behavior: the whole z.object (not just its .shape) is passed to the SDK, so zod 4
  .refine() checks on an input schema now actually run (they were silently skipped).
  This also makes .strict() objects reject unknown keys (JSON-RPC -32602; previously
  stripped) and .passthrough() objects forward them to the handler (previously stripped),
  and tools/list now reflects both via additionalProperties plus any object-level
  .describe(). Plain z.object schemas are advertised exactly as before.
• Behavior: onToolCall fires when a tool is invoked, concurrently with the handler
  (previously after it returned).
• Behavior: an error thrown by a mutating tool's preview or execute no longer reaches
  the client verbatim — throw ToolError for messages meant for the client.
• @modelcontextprotocol/sdk peer range raised from ^1 to ^1.25.0, the first release
  shipping the web-standard transport this kit imports.
• Untyped ToolDef handler input is unknown under zod 3 too (was any).
• Dependencies updated (vitest 5, hono 4.13, zod 4.6, SDK 1.30.1, eslint 10.11); npm run typecheck now also covers test/ and examples/.

Fixed

• Replaying confirm_request with the same idempotencyKey returned the cached result
  JSON-stringified inside a text block instead of the original result; a corrupt cached
  entry now yields a generic error instead of a parser message.
• A mutating tool whose side effect succeeded could be reported as failed — and its
  idempotency claim released, so a retry executed it twice — if its result couldn't be
  serialized or onMutation threw. Both now keep the claim and return success.
• An error thrown by a handler, preview, or execute, or a handler return value that
  couldn't be serialized (BigInt, cycles), leaked its raw message to the client.
• An object return value that merely has a content array (e.g. { id, content: [1, 2] })
  was passed through as a malformed tool result; it's now JSON-serialized.