Problem

AWS Bedrock requires tool names to match the pattern ^[a-zA-Z0-9_-]{1,128}$. MCP tools often have names containing dots and other special characters that violate this requirement, causing HTTP 400 errors when tool names are sent to Bedrock, which breaks the agent turn.

Solution

Implement tool name sanitization by:

1. Replacing invalid characters (especially dots) with underscores
2. Truncating names exceeding 128 characters
3. Maintaining a mapping from sanitized names back to original tool IDs
4. Resolving sanitized names to original IDs when executing tools

Changes

aibridge/intercept/messages/base.go

• Added sanitizedToolNames field to interceptionBase struct to track mapping
• Updated injectTools() method to sanitize tool names before sending to Bedrock
• Added sanitizeToolName() function that:
  • Replaces non-alphanumeric/non-underscore/non-hyphen characters with underscores
  • Truncates to 128 characters (Bedrock limit)
  • Returns "unknown_tool" for empty results
• Added resolveToolID() method to resolve sanitized names back to original IDs

aibridge/intercept/messages/blocking.go

• Updated tool lookup to use resolveToolID() before calling GetTool()
• Two locations updated: tool presence check and tool execution loop

aibridge/intercept/messages/streaming.go

• Updated 8 locations where tools are looked up to resolve sanitized names:
  • ContentBlockStart: block name resolution
  • ContentBlockDelta: lastToolName resolution
  • ContentBlockStop: lastToolName resolution
  • Message delta usage reporting
  • Tool name extraction from message content
  • Tool execution loop (name parameter iteration)
  • Non-injected tool tracking

aibridge/intercept/messages/base_internal_test.go

• Added comprehensive unit tests for sanitizeToolName() covering:
  • Empty strings → "unknown_tool"
  • Dots converted to underscores
  • Hyphens preserved
  • Mixed special characters handled
  • 128-character truncation
  • Edge cases

Testing

✅ All new unit tests pass (8 test cases for sanitizeToolName)
✅ Existing tests continue to pass
✅ Code formatting verified with go fmt

Example

sanitizeToolName("awslabs.aws_documentation_mcp_server__read_documentation")
// Returns: "awslabs_aws_documentation_mcp_server__read_documentation"

sanitizeToolName("@#$invalid!tool")
// Returns: "___invalid_tool"