Add docs for message sanitisation

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Sameer Kankute
2026-01-16 12:52:13 +05:30
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import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';
# Message Sanitization for Tool Calling for anthropic models
**Automatically fix common message formatting issues when using tool calling with `modify_params=True`**
LiteLLM can automatically sanitize messages to handle common issues that occur during tool calling workflows, especially when using OpenAI-compatible clients with providers that have strict message format requirements (like Anthropic Claude).
## Overview
When `litellm.modify_params = True` is enabled, LiteLLM automatically sanitizes messages to fix three common issues:
1. **Orphaned Tool Calls** - Assistant messages with tool_calls but missing tool results
2. **Orphaned Tool Results** - Tool messages that reference non-existent tool_call_ids
3. **Empty Message Content** - Messages with empty or whitespace-only text content
This ensures your tool calling workflows work seamlessly across different LLM providers without manual message validation.
## Why Message Sanitization?
Different LLM providers have varying requirements for message formats, especially during tool calling:
- **Anthropic Claude** requires every tool_call to have a corresponding tool result
- Some providers reject messages with empty content
- OpenAI-compatible clients may not always maintain perfect message consistency
Without sanitization, these issues cause API errors that interrupt your workflows. With `modify_params=True`, LiteLLM handles these edge cases automatically.
## Quick Start
<Tabs>
<TabItem value="sdk" label="SDK">
```python
import litellm
# Enable automatic message sanitization
litellm.modify_params = True
# This will work even if messages have formatting issues
response = litellm.completion(
model="anthropic/claude-3-5-sonnet-20241022",
messages=[
{"role": "user", "content": "What's the weather in Boston?"},
{
"role": "assistant",
"tool_calls": [
{
"id": "call_123",
"type": "function",
"function": {"name": "get_weather", "arguments": '{"city": "Boston"}'}
}
]
# Missing tool result - LiteLLM will add a dummy result automatically
},
{"role": "user", "content": "Thanks!"}
],
tools=[{
"type": "function",
"function": {
"name": "get_weather",
"description": "Get weather for a city",
"parameters": {
"type": "object",
"properties": {"city": {"type": "string"}},
"required": ["city"]
}
}
}]
)
```
</TabItem>
<TabItem value="proxy" label="PROXY">
```yaml
litellm_settings:
modify_params: true # Enable automatic message sanitization
model_list:
- model_name: claude-3-5-sonnet
litellm_params:
model: anthropic/claude-3-5-sonnet-20241022
```
</TabItem>
</Tabs>
## Sanitization Cases
### Case A: Orphaned Tool Calls (Missing Tool Results)
**Problem:** An assistant message contains `tool_calls`, but no corresponding tool result messages follow.
**Solution:** LiteLLM automatically adds dummy tool result messages for any missing tool results.
**Example:**
```python
import litellm
litellm.modify_params = True
# Messages with orphaned tool calls
messages = [
{"role": "user", "content": "Search for Python tutorials"},
{
"role": "assistant",
"tool_calls": [
{
"id": "call_abc123",
"type": "function",
"function": {"name": "web_search", "arguments": '{"query": "Python tutorials"}'}
}
]
},
# Missing tool result here!
{"role": "user", "content": "What about JavaScript?"}
]
# LiteLLM automatically adds:
# {
# "role": "tool",
# "tool_call_id": "call_abc123",
# "content": "[System: Tool execution skipped/interrupted by user. No result provided for tool 'web_search'.]"
# }
response = litellm.completion(
model="anthropic/claude-3-5-sonnet-20241022",
messages=messages,
tools=[...]
)
```
**When this happens:**
- User interrupts tool execution
- Client loses tool results due to network issues
- Conversation flow changes before tool completes
- Multi-turn conversations where tools are optional
### Case B: Orphaned Tool Results (Invalid tool_call_id)
**Problem:** A tool message references a `tool_call_id` that doesn't exist in any previous assistant message.
**Solution:** LiteLLM automatically removes these orphaned tool result messages.
**Example:**
```python
import litellm
litellm.modify_params = True
# Messages with orphaned tool result
messages = [
{"role": "user", "content": "Hello"},
{"role": "assistant", "content": "Hi! How can I help?"},
{
"role": "tool",
"tool_call_id": "call_nonexistent", # This tool_call_id doesn't exist!
"content": "Some result"
}
]
# LiteLLM automatically removes the orphaned tool message
response = litellm.completion(
model="anthropic/claude-3-5-sonnet-20241022",
messages=messages
)
```
**When this happens:**
- Message history is manually edited
- Tool results are duplicated or mismatched
- Conversation state is restored incorrectly
- Messages are merged from different conversations
### Case C: Empty Message Content
**Problem:** User or assistant messages have empty or whitespace-only content.
**Solution:** LiteLLM replaces empty content with a system placeholder message.
**Example:**
```python
import litellm
litellm.modify_params = True
# Messages with empty content
messages = [
{"role": "user", "content": ""}, # Empty content
{"role": "assistant", "content": " "}, # Whitespace only
]
# LiteLLM automatically replaces with:
# {"role": "user", "content": "[System: Empty message content sanitised to satisfy protocol]"}
# {"role": "assistant", "content": "[System: Empty message content sanitised to satisfy protocol]"}
response = litellm.completion(
model="anthropic/claude-3-5-sonnet-20241022",
messages=messages
)
```
**When this happens:**
- UI sends empty messages
- Content is stripped during preprocessing
- Placeholder messages in conversation history
- Edge cases in message construction
## Configuration
### Enable Globally
<Tabs>
<TabItem value="sdk" label="SDK">
```python
import litellm
# Enable for all completion calls
litellm.modify_params = True
```
</TabItem>
<TabItem value="proxy" label="PROXY">
```yaml
litellm_settings:
modify_params: true
```
</TabItem>
<TabItem value="env" label="Environment Variable">
```bash
export LITELLM_MODIFY_PARAMS=True
```
</TabItem>
</Tabs>
### Enable Per-Request
```python
import litellm
# Enable only for specific requests
response = litellm.completion(
model="anthropic/claude-3-5-sonnet-20241022",
messages=messages,
modify_params=True # Override global setting
)
```
## Supported Providers
Message sanitization works with all LLM providers that support tool calling:
- ✅ Anthropic (Claude)
- ✅ OpenAI (GPT-4, GPT-3.5)
- ✅ AWS Bedrock (Claude, Titan)
- ✅ Google Vertex AI (Claude, Gemini)
- ✅ Azure OpenAI
- ✅ And all other providers with tool calling support
## Implementation Details
### How It Works
The message sanitization process runs **before** messages are converted to provider-specific formats:
1. **Input:** OpenAI-format messages with potential issues
2. **Sanitization:** Three helper functions process the messages:
- `_sanitize_empty_text_content()` - Fixes empty content
- `_add_missing_tool_results()` - Adds dummy tool results
- `_is_orphaned_tool_result()` - Identifies orphaned results
3. **Output:** Clean, provider-compatible messages
### Code Reference
The sanitization logic is implemented in:
- `litellm/litellm_core_utils/prompt_templates/factory.py`
- Function: `sanitize_messages_for_tool_calling()`
### Logging
When sanitization occurs, LiteLLM logs debug messages:
```python
import litellm
litellm.set_verbose = True # Enable debug logging
# You'll see logs like:
# "_add_missing_tool_results: Found 1 orphaned tool calls. Adding dummy tool results."
# "_is_orphaned_tool_result: Found orphaned tool result with tool_call_id=call_123"
# "_sanitize_empty_text_content: Replaced empty text content in user message"
```
## Best Practices
### 1. Enable for Production Workflows
```python
# Recommended for production
litellm.modify_params = True
# Ensures robust handling of edge cases
response = litellm.completion(
model="anthropic/claude-3-5-sonnet-20241022",
messages=messages,
tools=tools
)
```
### 2. Preserve Tool Results When Possible
While sanitization handles missing tool results, it's better to provide actual results:
```python
# Good: Provide actual tool results
messages = [
{"role": "user", "content": "Search for Python"},
{"role": "assistant", "tool_calls": [...]},
{"role": "tool", "tool_call_id": "call_123", "content": "Actual search results"}
]
# Fallback: Sanitization adds dummy result if missing
messages = [
{"role": "user", "content": "Search for Python"},
{"role": "assistant", "tool_calls": [...]},
# Missing tool result - sanitization adds dummy
]
```
### 3. Monitor Sanitization Events
Use logging to track when sanitization occurs:
```python
import litellm
import logging
# Enable debug logging
litellm.set_verbose = True
logging.basicConfig(level=logging.DEBUG)
# Track sanitization events in your application
response = litellm.completion(
model="anthropic/claude-3-5-sonnet-20241022",
messages=messages
)
```
### 4. Test Edge Cases
Ensure your application handles sanitized messages correctly:
```python
import litellm
litellm.modify_params = True
# Test orphaned tool calls
test_messages = [
{"role": "user", "content": "Test"},
{"role": "assistant", "tool_calls": [{"id": "call_1", "type": "function", "function": {"name": "test", "arguments": "{}"}}]},
{"role": "user", "content": "Continue"} # No tool result
]
response = litellm.completion(
model="anthropic/claude-3-5-sonnet-20241022",
messages=test_messages,
tools=[...]
)
# Verify the response handles the dummy tool result appropriately
```
## Related Features
- **[Drop Params](./drop_params.md)** - Drop unsupported parameters for specific providers
- **[Message Trimming](./message_trimming.md)** - Trim messages to fit token limits
- **[Function Calling](./function_call.md)** - Complete guide to tool/function calling
- **[Reasoning Content](../reasoning_content.md)** - Extended thinking with tool calling
## Troubleshooting
### Sanitization Not Working
**Issue:** Messages still cause errors despite `modify_params=True`
**Solution:**
1. Verify `modify_params` is enabled:
```python
import litellm
print(litellm.modify_params) # Should be True
```
2. Check if the issue is provider-specific:
```python
litellm.set_verbose = True # Enable debug logging
```
3. Ensure you're using a recent version of LiteLLM:
```bash
pip install --upgrade litellm
```
### Unexpected Dummy Tool Results
**Issue:** Dummy tool results appear when you expect actual results
**Cause:** Tool result messages are missing or have incorrect `tool_call_id`
**Solution:**
1. Verify tool result messages have correct `tool_call_id`:
```python
# Correct
{"role": "tool", "tool_call_id": "call_123", "content": "result"}
# Incorrect - will be treated as orphaned
{"role": "tool", "tool_call_id": "wrong_id", "content": "result"}
```
2. Ensure tool results immediately follow assistant messages with tool_calls
### Performance Impact
**Issue:** Concerned about performance overhead
**Details:** Message sanitization has minimal performance impact:
- Runs in O(n) time where n = number of messages
- Only processes messages when `modify_params=True`
- Typically adds < 1ms to request processing time
## FAQ
**Q: Does sanitization modify my original messages?**
A: No, sanitization creates a new list of messages. Your original messages remain unchanged.
**Q: Can I disable specific sanitization cases?**
A: Currently, all three cases are handled together when `modify_params=True`. To disable sanitization entirely, set `modify_params=False`.
**Q: What happens to the dummy tool results?**
A: Dummy tool results are sent to the LLM provider along with other messages. The model sees them as regular tool results with informative error messages.
**Q: Does this work with streaming?**
A: Yes, message sanitization works with both streaming and non-streaming requests.
**Q: Is this related to `drop_params`?**
A: No, they're separate features:
- `modify_params` - Modifies/fixes message content and structure
- `drop_params` - Removes unsupported API parameters
Both can be enabled simultaneously.
## See Also
- [Reasoning Content with Tool Calling](../reasoning_content.md)
- [Function Calling Guide](./function_call.md)
- [Bedrock Provider Documentation](../providers/bedrock.md)
- [Anthropic Provider Documentation](../providers/anthropic.md)
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@@ -937,6 +937,7 @@ const sidebars = {
"providers/anthropic_tool_search",
"guides/code_interpreter",
"completion/message_trimming",
"completion/message_sanitization",
"completion/model_alias",
"completion/mock_requests",
"completion/predict_outputs",