Adding Anthropic support and test coverage

Author: Artui

pydantic_ai_slim/pydantic_ai/models/anthropic.py

@@ -68,6 +68,8 @@
         BetaContentBlockParam,
         BetaImageBlockParam,
         BetaInputJSONDelta,
+        BetaMCPToolResultBlock,
+        BetaMCPToolUseBlock,
         BetaMemoryTool20250818Param,
         BetaMessage,
         BetaMessageParam,
@@ -267,7 +269,7 @@ async def _messages_create(
         # standalone function to make it easier to override
         tools = self._get_tools(model_request_parameters)
         tools, beta_features = self._add_builtin_tools(tools, model_request_parameters)
-        mcp_servers = self._get_mcp_servers(model_request_parameters)
+        mcp_servers, beta_features = self._get_mcp_servers(model_request_parameters, beta_features)
 
         tool_choice: BetaToolChoiceParam | None
 
@@ -323,6 +325,8 @@ def _process_response(self, response: BetaMessage) -> ModelResponse:
         """Process a non-streamed response, and prepare a message to return."""
         items: list[ModelResponsePart] = []
         for item in response.content:
+            from anthropic.types.beta import BetaMCPToolUseBlock
+
             if isinstance(item, BetaTextBlock):
                 items.append(TextPart(content=item.text))
             elif isinstance(item, BetaServerToolUseBlock):
@@ -337,6 +341,10 @@ def _process_response(self, response: BetaMessage) -> ModelResponse:
                 )
             elif isinstance(item, BetaThinkingBlock):
                 items.append(ThinkingPart(content=item.thinking, signature=item.signature, provider_name=self.system))
+            elif isinstance(item, BetaMCPToolUseBlock):
+                items.append(_map_mcp_server_use_block(item, self.system))
+            elif isinstance(item, BetaMCPToolResultBlock):
+                items.append(_map_mcp_server_result_block(item, self.system))
             else:
                 assert isinstance(item, BetaToolUseBlock), f'unexpected item type {type(item)}'
                 items.append(
@@ -421,18 +429,14 @@ def _add_builtin_tools(
         return tools, beta_features
 
     def _get_mcp_servers(
-        self, model_request_parameters: ModelRequestParameters
-    ) -> list[BetaRequestMCPServerURLDefinitionParam]:
+        self, model_request_parameters: ModelRequestParameters, beta_features: list[str]
+    ) -> tuple[list[BetaRequestMCPServerURLDefinitionParam], list[str]]:
         mcp_servers: list[BetaRequestMCPServerURLDefinitionParam] = []
         for tool in model_request_parameters.builtin_tools:
             if isinstance(tool, MCPServerTool):
-                tool_configuration = (
-                    BetaRequestMCPServerToolConfigurationParam(
-                        enabled=True,
-                        allowed_tools=tool.allowed_tools,
-                    )
-                    if tool.allowed_tools
-                    else None
+                tool_configuration = BetaRequestMCPServerToolConfigurationParam(
+                    enabled=True,
+                    allowed_tools=tool.allowed_tools,
                 )
                 mcp_servers.append(
                     BetaRequestMCPServerURLDefinitionParam(
@@ -443,7 +447,8 @@ def _get_mcp_servers(
                         tool_configuration=tool_configuration,
                     )
                 )
-        return mcp_servers
+                beta_features.append('mcp-client-2025-04-04')
+        return mcp_servers, beta_features
 
     async def _map_message(self, messages: list[ModelMessage]) -> tuple[str, list[BetaMessageParam]]:  # noqa: C901
         """Just maps a `pydantic_ai.Message` to a `anthropic.types.MessageParam`."""
@@ -743,6 +748,16 @@ async def _get_event_iterator(self) -> AsyncIterator[ModelResponseStreamEvent]:
                         vendor_part_id=event.index,
                         part=_map_code_execution_tool_result_block(current_block, self.provider_name),
                     )
+                elif isinstance(current_block, BetaMCPToolUseBlock):
+                    yield self._parts_manager.handle_part(
+                        vendor_part_id=event.index,
+                        part=_map_mcp_server_use_block(current_block, self.provider_name),
+                    )
+                elif isinstance(current_block, BetaMCPToolResultBlock):
+                    yield self._parts_manager.handle_part(
+                        vendor_part_id=event.index,
+                        part=_map_mcp_server_result_block(current_block, self.provider_name),
+                    )
 
             elif isinstance(event, BetaRawContentBlockDeltaEvent):
                 if isinstance(event.delta, BetaTextDelta):
@@ -848,3 +863,21 @@ def _map_code_execution_tool_result_block(
         content=code_execution_tool_result_content_ta.dump_python(item.content, mode='json'),
         tool_call_id=item.tool_use_id,
     )
+
+
+def _map_mcp_server_use_block(item: BetaMCPToolUseBlock, provider_name: str) -> BuiltinToolCallPart:
+    return BuiltinToolCallPart(
+        provider_name=provider_name,
+        tool_name=MCPServerTool.kind,
+        args=cast(dict[str, Any], item.input) or None,
+        tool_call_id=item.id,
+    )
+
+
+def _map_mcp_server_result_block(item: BetaMCPToolResultBlock, provider_name: str) -> BuiltinToolReturnPart:
+    return BuiltinToolReturnPart(
+        provider_name=provider_name,
+        tool_name=CodeExecutionTool.kind,
+        content=item.content,
+        tool_call_id=item.tool_use_id,
+    )

tests/models/cassettes/test_anthropic/test_anthropic_mcp_servers.yaml

@@ -0,0 +1,101 @@
+interactions:
+- request:
+    headers:
+      accept:
+      - application/json
+      accept-encoding:
+      - gzip, deflate
+      connection:
+      - keep-alive
+      content-length:
+      - '406'
+      content-type:
+      - application/json
+      host:
+      - api.anthropic.com
+    method: POST
+    parsed_body:
+      max_tokens: 4096
+      mcp_servers:
+      - authorization_token: ''
+        name: test-server
+        tool_configuration:
+          allowed_tools:
+          - get_my_games
+          enabled: true
+        type: url
+        url: https://example.com/mcp
+      messages:
+      - content:
+        - text: What games do I have?
+          type: text
+        role: user
+      model: claude-sonnet-4-0
+      stream: false
+      thinking:
+        budget_tokens: 3000
+        type: enabled
+    uri: https://api.anthropic.com/v1/messages?beta=true
+  response:
+    headers:
+      connection:
+      - keep-alive
+      content-length:
+      - '2260'
+      content-type:
+      - application/json
+      strict-transport-security:
+      - max-age=31536000; includeSubDomains; preload
+      transfer-encoding:
+      - chunked
+    parsed_body:
+      content:
+      - signature: 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
+        thinking: The user is asking what games they have. I have a function available called "test-server_get_my_games" that
+          returns a list of the user's favorite games. This seems like the appropriate function to call to answer their question.
+          The function doesn't require any parameters according to the schema, so I can call it directly.
+        type: thinking
+      - text: I'll check what games you have by looking up your game list.
+        type: text
+      - id: mcptoolu_01TwwBu8ALMaffJS5riJmE8r
+        input: {}
+        name: get_my_games
+        server_name: test-server
+        type: mcp_tool_use
+      - content:
+        - text: '["Lies of P","Bloodborne","Sekiro"]'
+          type: text
+        is_error: false
+        tool_use_id: mcptoolu_01TwwBu8ALMaffJS5riJmE8r
+        type: mcp_tool_result
+      - text: |-
+          Based on your game library, you have these games:
+
+          1. **Lies of P** - A dark fantasy soulslike game inspired by Pinocchio
+          2. **Bloodborne** - FromSoftware's gothic horror action RPG
+          3. **Sekiro** - FromSoftware's ninja-themed action-adventure game
+
+          It looks like you have a great collection of challenging action games, particularly from the soulslike genre!
+        type: text
+      id: msg_01T1PQHnUHVDevzQSm91GmVP
+      model: claude-sonnet-4-20250514
+      role: assistant
+      stop_reason: end_turn
+      stop_sequence: null
+      type: message
+      usage:
+        cache_creation:
+          ephemeral_1h_input_tokens: 0
+          ephemeral_5m_input_tokens: 0
+        cache_creation_input_tokens: 0
+        cache_read_input_tokens: 0
+        input_tokens: 965
+        output_tokens: 234
+        server_tool_use:
+          web_fetch_requests: 0
+          web_search_requests: 0
+        service_tier: standard
+    status:
+      code: 200
+      message: OK
+version: 1

tests/models/cassettes/test_anthropic/test_anthropic_mcp_servers_stream.yaml

@@ -0,0 +1,137 @@
+interactions:
+- request:
+    headers:
+      accept:
+      - application/json
+      accept-encoding:
+      - gzip, deflate
+      connection:
+      - keep-alive
+      content-length:
+      - '393'
+      content-type:
+      - application/json
+      host:
+      - api.anthropic.com
+    method: POST
+    parsed_body:
+      max_tokens: 4096
+      mcp_servers:
+      - authorization_token: ''
+        name: test-server
+        tool_configuration:
+          allowed_tools: null
+          enabled: true
+        type: url
+        url: https://example.com/mcp
+      messages:
+      - content:
+        - text: What games do I have?
+          type: text
+        role: user
+      model: claude-sonnet-4-5
+      stream: true
+      thinking:
+        budget_tokens: 3000
+        type: enabled
+    uri: https://api.anthropic.com/v1/messages?beta=true
+  response:
+    body:
+      string: |+
+        event: message_start
+        data: {"type":"message_start","message":{"model":"claude-sonnet-4-5-20250929","id":"msg_012dGSyGXMqFnc6yNfYPq9Qe","type":"message","role":"assistant","content":[],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":585,"cache_creation_input_tokens":0,"cache_read_input_tokens":0,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":0},"output_tokens":8,"service_tier":"standard"}}  }
+
+        event: content_block_start
+        data: {"type":"content_block_start","index":0,"content_block":{"type":"thinking","thinking":"","signature":""} }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":0,"delta":{"type":"thinking_delta","thinking":"The user is asking about their games"}       }
+
+        event: ping
+        data: {"type": "ping"}
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":0,"delta":{"type":"thinking_delta","thinking":". I have a function called `test-server_"}    }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":0,"delta":{"type":"thinking_delta","thinking":"get_my_games` that returns"}        }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":0,"delta":{"type":"thinking_delta","thinking":" a list of the user's favorite games. This function doesn't require any parameters,"}    }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":0,"delta":{"type":"thinking_delta","thinking":" so I can call it directly."}     }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":0,"delta":{"type":"signature_delta","signature":"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"}       }
+
+        event: content_block_stop
+        data: {"type":"content_block_stop","index":0   }
+
+        event: content_block_start
+        data: {"type":"content_block_start","index":1,"content_block":{"type":"mcp_tool_use","id":"mcptoolu_01WaYLgtwyroxT1CQWGFfTTy","name":"get_my_games","input":{},"server_name":"test-server"}      }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":1,"delta":{"type":"input_json_delta","partial_json":""}              }
+
+        event: content_block_stop
+        data: {"type":"content_block_stop","index":1    }
+
+        event: content_block_start
+        data: {"type":"content_block_start","index":2,"content_block":{"type":"mcp_tool_result","tool_use_id":"mcptoolu_01WaYLgtwyroxT1CQWGFfTTy","is_error":false,"content":[{"type":"text","text":"[\"Lies of P\",\"Bloodborne\",\"Sekiro\"]"}]}            }
+
+        event: content_block_stop
+        data: {"type":"content_block_stop","index":2            }
+
+        event: content_block_start
+        data: {"type":"content_block_start","index":3,"content_block":{"type":"text","text":""}           }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":3,"delta":{"type":"text_delta","text":"You"}          }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":3,"delta":{"type":"text_delta","text":" have the following games:\n1. Lies"}    }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":3,"delta":{"type":"text_delta","text":" of P\n2. Bloodborne"}      }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":3,"delta":{"type":"text_delta","text":"\n3. Sekiro\n\nThese"}   }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":3,"delta":{"type":"text_delta","text":" are all excellent action games known for their challenging combat"}             }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":3,"delta":{"type":"text_delta","text":"! It looks like you have a strong preference"}       }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":3,"delta":{"type":"text_delta","text":" for souls-like and FromSoftware titles"}         }
+
+        event: content_block_delta
+        data: {"type":"content_block_delta","index":3,"delta":{"type":"text_delta","text":"."}     }
+
+        event: content_block_stop
+        data: {"type":"content_block_stop","index":3    }
+
+        event: message_delta
+        data: {"type":"message_delta","delta":{"stop_reason":"end_turn","stop_sequence":null},"usage":{"input_tokens":1297,"cache_creation_input_tokens":0,"cache_read_input_tokens":0,"output_tokens":161,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0}}      }
+
+        event: message_stop
+        data: {"type":"message_stop"               }
+
+    headers:
+      cache-control:
+      - no-cache
+      connection:
+      - keep-alive
+      content-type:
+      - text/event-stream; charset=utf-8
+      strict-transport-security:
+      - max-age=31536000; includeSubDomains; preload
+      transfer-encoding:
+      - chunked
+    status:
+      code: 200
+      message: OK
+version: 1
+...