fix(tools): add omitempty to properties (#116)

jkoelker · web-flow · commit 7335e3a843cf · 2025-04-16T20:46:34.000+03:00
When there is no input to a tool, the `Properies` map is `nil` if the Tool is not created using `NewTool`. This causes the `property` field to be set to `null` and clients such as `claude-desktop` to skip the tools silently. Annotating the field as `omitempty` is inline with the behavior of the [typescript-sdk](https://github.com/modelcontextprotocol/typescript-sdk/blob/fbdeb06a4185ba2f7581603a768cd7171c64d6fc/src/types.ts#L749).
diff --git a/mcp/tools.go b/mcp/tools.go
@@ -105,7 +105,7 @@ func (t Tool) MarshalJSON() ([]byte, error) {
 
 type ToolInputSchema struct {
 	Type       string                 `json:"type"`
-	Properties map[string]interface{} `json:"properties"`
+	Properties map[string]interface{} `json:"properties,omitempty"`
 	Required   []string               `json:"required,omitempty"`
 }
 

Original file line number	Diff line number	Diff line change
`@@ -105,7 +105,7 @@ func (t Tool) MarshalJSON() ([]byte, error) {`
`105`	`105`
`106`	`106`	`type ToolInputSchema struct {`
`107`	`107`	Type string `json:"type"`
`108`		- Properties map[string]interface{} `json:"properties"`
	`108`	+ Properties map[string]interface{} `json:"properties,omitempty"`
`109`	`109`	Required []string `json:"required,omitempty"`
`110`	`110`	`}`
`111`	`111`