docs: add parallel tool calling docs (#5876)

* docs: add parallel tool calling docs

* docs: forgot the yaml

* fix: update

fern/docs.yml

@@ -152,6 +152,8 @@ navigation:
                 path: pages/agents/fetch_webpage.mdx
           - page: Custom Tools
             path: pages/agents/custom_tools.mdx
+          - page: Parallel Tool Calling
+            path: pages/agents/parallel_tool_calling.mdx
           - page: Tool Rules
             path: pages/agents/tool_rules.mdx
           - page: Tool Variables

fern/pages/agents/parallel_tool_calling.mdx

@@ -0,0 +1,102 @@
+---
+title: Parallel Tool Calling
+slug: guides/agents/parallel-tool-calling
+---
+
+When an agent calls multiple tools, Letta can execute them concurrently instead of sequentially.
+
+Parallel tool calling has two configuration levels:
+- **Agent LLM config**: Controls whether the LLM can request multiple tool calls at once
+- **Individual tool settings**: Controls whether requested tools actually execute in parallel or sequentially
+
+## Model Support
+
+Parallel tool calling is supported for OpenAI and Anthropic models.
+
+## Enabling Parallel Tool Calling
+
+### Agent Configuration
+
+Set `parallel_tool_calls: true` in the agent's LLM config:
+
+<CodeGroup>
+```typescript TypeScript
+const agent = await client.agents.create({
+  llm_config: {
+    model: "anthropic/claude-sonnet-4-20250514",
+    parallel_tool_calls: true
+  }
+});
+```
+```python Python
+agent = client.agents.create(
+    llm_config={
+        "model": "anthropic/claude-sonnet-4-20250514",
+        "parallel_tool_calls": True
+    }
+)
+```
+</CodeGroup>
+
+### Tool Configuration
+
+Individual tools must opt-in to parallel execution:
+
+<CodeGroup>
+```typescript TypeScript
+await client.tools.update(toolId, {
+  enable_parallel_execution: true
+});
+```
+```python Python
+client.tools.update(
+    tool_id=tool_id,
+    enable_parallel_execution=True
+)
+```
+</CodeGroup>
+
+By default, tools execute sequentially (`enable_parallel_execution=False`).
+
+<Warning>
+Only enable parallel execution for tools safe to run concurrently. Tools that modify shared state or have ordering dependencies should remain sequential.
+</Warning>
+
+## ADE Configuration
+
+### Agent Toggle
+
+1. Open **Settings** → **LLM Config**
+2. Enable **"Parallel tool calls"**
+
+### Tool Toggle
+
+1. Open the **Tools** panel
+2. Click a tool to open it
+3. Go to the **Settings** tab
+4. Enable **"Enable parallel execution"**
+
+## Execution Behavior
+
+When the agent calls multiple tools:
+- Sequential tools execute one-by-one
+- Parallel-enabled tools execute concurrently
+- Mixed: sequential tools complete first, then parallel tools execute together
+
+Example:
+```
+Agent calls:
+  - search_web (parallel: true)
+  - search_database (parallel: true)
+  - send_message (parallel: false)
+
+Execution:
+  1. send_message executes
+  2. search_web AND search_database execute concurrently
+```
+
+## Limitations
+
+- Parallel execution is automatically disabled when [tool rules](/guides/agents/tool-rules) are configured
+- Only enable for tools safe to run concurrently (e.g., read-only operations)
+- Tools that modify shared state should remain sequential