diff --git a/mcp/idempotency.yaml b/mcp/idempotency.yaml
index aeb7139..521df35 100644
--- a/mcp/idempotency.yaml
+++ b/mcp/idempotency.yaml
@@ -46,3 +46,83 @@ rules:
       Accept an idempotency key parameter (idempotency_key / request_id) and
       de-duplicate server-side so a retried call is a no-op after the first
       success.
+
+  - id: MCP-027
+    title: TypeScript MCP mutating tool has no idempotency key
+    severity: medium
+    confidence: 0.5
+    language: typescript
+    applies_to:
+      - mcp_tool
+    scope: tool
+    match:
+      all:
+        - name_has_prefix:
+            - create
+            - send
+            - delete
+            - post
+            - update
+            - refund
+            - charge
+            - issue
+        - not:
+            param_name_matches:
+              contains:
+                - idempot
+              exact:
+                - requestId
+                - request_id
+                - txnId
+                - txn_id
+    explanation: >
+      This TypeScript MCP tool's name implies a side effect (create/send/refund/…)
+      but its inputSchema exposes no idempotency parameter. MCP clients retry
+      tool calls under timeouts and ambiguous failures, the model may repeat the
+      action when a result reads as inconclusive, and a lost response after the
+      side effect committed is at-least-once delivery — so the same charge, send,
+      or delete can fire twice. Without a key the connecting client cannot make
+      the retry safe. The prefix set matches both `create_charge` and
+      `createCharge` naming, so it fires on idiomatic TypeScript tool names.
+    fix: >
+      Add an `idempotencyKey` (or `requestId`) field to the tool's inputSchema,
+      thread it to the downstream API, and confirm that API treats a repeated
+      key as a no-op rather than a second mutation.
+
+  - id: MCP-029
+    title: PHP MCP mutating tool has no idempotency key
+    severity: medium
+    confidence: 0.55
+    language: php
+    applies_to:
+      - mcp_tool
+    scope: tool
+    match:
+      all:
+        - name_has_prefix:
+            - create_
+            - send_
+            - delete_
+            - post_
+            - update_
+            - refund_
+            - charge_
+            - issue_
+        - not:
+            param_name_matches:
+              contains:
+                - idempot
+              exact:
+                - request_id
+                - txn_id
+    explanation: >
+      This PHP MCP tool's name signals a side effect (create/send/refund/…) but
+      the handler takes no idempotency-key parameter. MCP clients retry tool
+      calls under timeouts and ambiguous failures, and a lost response after the
+      side effect committed is at-least-once delivery — so the same charge,
+      order, or message can fire twice. Without a key the handler executes the
+      mutation twice.
+    fix: >
+      Accept an idempotency key parameter (idempotency_key / request_id) on the
+      #[McpTool] method and de-duplicate server-side so a retried call is a
+      no-op after the first success.
diff --git a/mcp/tool_definition.yaml b/mcp/tool_definition.yaml
index 1e84312..fb9f52b 100644
--- a/mcp/tool_definition.yaml
+++ b/mcp/tool_definition.yaml
@@ -309,3 +309,34 @@ rules:
     fix: >
       Rename the method (or set the `#[tool]` `name = "..."` argument) to a
       verb-object form, e.g. `summarize_invoice`, `fetch_weather`.
+
+  - id: MCP-028
+    title: Ambiguous TypeScript MCP tool name
+    severity: low
+    confidence: 0.85
+    language: typescript
+    applies_to:
+      - mcp_tool
+    scope: tool
+    match:
+      name_in:
+        - process
+        - handle
+        - run
+        - do
+        - execute
+        - perform
+        - work
+        - go
+        - thing
+        - stuff
+    explanation: >
+      A TypeScript MCP tool's name is the first argument to
+      `server.registerTool(...)` (or the legacy `server.tool(...)`). Names like
+      `process`, `handle`, or `run` give a connecting model no signal about
+      intent. Because an MCP server is consumed by clients the author does not
+      control, an ambiguous name degrades tool selection everywhere the server is
+      mounted and collides more easily with similarly-named tools from other
+      servers in the same session.
+    fix: >
+      Rename to a verb-object form, e.g. `summarizeInvoice`, `fetchWeather`.