feat(tools): Add valueFromParam support to Tool config (googleapis#2333)

This PR introduces a new configuration field valueFromParam to the tool
definitions. This feature allows a parameter to automatically inherit
its value from another sibling parameter, mainly to streamline the
configuration of vector insertion tools.

Parameters utilizing valueFromParam are excluded from the Tool and MCP
manifests. This means the LLM does not see these parameters and is not
required to generate them. The value is resolved internally by the
Toolbox during execution.

Author: duwenxin99

cmd/root_test.go

@@ -2181,3 +2181,115 @@ func TestDefaultToolsFileBehavior(t *testing.T) {
 		})
 	}
 }
+
+func TestParameterReferenceValidation(t *testing.T) {
+	ctx, err := testutils.ContextWithNewLogger()
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	// Base template
+	baseYaml := `
+sources:
+  dummy-source:
+    kind: http
+    baseUrl: http://example.com
+tools:
+  test-tool:
+    kind: postgres-sql
+    source: dummy-source
+    description: test tool
+    statement: SELECT 1;
+    parameters:
+%s`
+
+	tcs := []struct {
+		desc      string
+		params    string
+		wantErr   bool
+		errSubstr string
+	}{
+		{
+			desc: "valid backward reference",
+			params: `
+      - name: source_param
+        type: string
+        description: source
+      - name: copy_param
+        type: string
+        description: copy
+        valueFromParam: source_param`,
+			wantErr: false,
+		},
+		{
+			desc: "valid forward reference (out of order)",
+			params: `
+      - name: copy_param
+        type: string
+        description: copy
+        valueFromParam: source_param
+      - name: source_param
+        type: string
+        description: source`,
+			wantErr: false,
+		},
+		{
+			desc: "invalid missing reference",
+			params: `
+      - name: copy_param
+        type: string
+        description: copy
+        valueFromParam: non_existent_param`,
+			wantErr:   true,
+			errSubstr: "references '\"non_existent_param\"' in the 'valueFromParam' field",
+		},
+		{
+			desc: "invalid self reference",
+			params: `
+      - name: myself
+        type: string
+        description: self
+        valueFromParam: myself`,
+			wantErr:   true,
+			errSubstr: "parameter \"myself\" cannot copy value from itself",
+		},
+		{
+			desc: "multiple valid references",
+			params: `
+      - name: a
+        type: string
+        description: a
+      - name: b
+        type: string
+        description: b
+        valueFromParam: a
+      - name: c
+        type: string
+        description: c
+        valueFromParam: a`,
+			wantErr: false,
+		},
+	}
+
+	for _, tc := range tcs {
+		t.Run(tc.desc, func(t *testing.T) {
+			// Indent parameters to match YAML structure
+			yamlContent := fmt.Sprintf(baseYaml, tc.params)
+
+			_, err := parseToolsFile(ctx, []byte(yamlContent))
+
+			if tc.wantErr {
+				if err == nil {
+					t.Fatal("expected error, got nil")
+				}
+				if !strings.Contains(err.Error(), tc.errSubstr) {
+					t.Errorf("error %q does not contain expected substring %q", err.Error(), tc.errSubstr)
+				}
+			} else {
+				if err != nil {
+					t.Fatalf("unexpected error: %v", err)
+				}
+			}
+		})
+	}
+}

docs/en/resources/embeddingModels/_index.md

@@ -3,13 +3,14 @@ title: "EmbeddingModels"
 type: docs
 weight: 2
 description: >
-  EmbeddingModels represent services that transform text into vector embeddings for semantic search.
+  EmbeddingModels represent services that transform text into vector embeddings
+  for semantic search.
 ---
 
 EmbeddingModels represent services that generate vector representations of text
-data. In the MCP Toolbox, these models enable **Semantic Queries**,
-allowing [Tools](../tools/) to automatically convert human-readable text into
-numerical vectors before using them in a query.
+data. In the MCP Toolbox, these models enable **Semantic Queries**, allowing
+[Tools](../tools/) to automatically convert human-readable text into numerical
+vectors before using them in a query.
 
 This is primarily used in two scenarios:
 
@@ -19,14 +20,33 @@ This is primarily used in two scenarios:
 - **Semantic Search**: Converting a natural language query into a vector to
   perform similarity searches.
 
+## Hidden Parameter Duplication (valueFromParam)
+
+When building tools for vector ingestion, you often need the same input string
+twice:
+
+1. To store the original text in a TEXT column.
+1. To generate the vector embedding for a VECTOR column.
+
+Requesting an Agent (LLM) to output the exact same string twice is inefficient
+and error-prone. The `valueFromParam` field solves this by allowing a parameter
+to inherit its value from another parameter in the same tool.
+
+### Key Behaviors
+
+1. Hidden from Manifest: Parameters with valueFromParam set are excluded from
+   the tool definition sent to the Agent. The Agent does not know this parameter
+   exists.
+1. Auto-Filled: When the tool is executed, the Toolbox automatically copies the
+   value from the referenced parameter before processing embeddings.
+
 ## Example
 
 The following configuration defines an embedding model and applies it to
 specific tool parameters.
 
-{{< notice tip >}}
-Use environment variable replacement with the format ${ENV_NAME}
-instead of hardcoding your API keys into the configuration file.
+{{< notice tip >}} Use environment variable replacement with the format
+${ENV_NAME} instead of hardcoding your API keys into the configuration file.
 {{< /notice >}}
 
 ### Step 1 - Define an Embedding Model
@@ -40,14 +60,12 @@ embeddingModels:
     model: gemini-embedding-001
     apiKey: ${GOOGLE_API_KEY}
     dimension: 768
-
 ```
 
 ### Step 2 - Embed Tool Parameters
 
 Use the defined embedding model, embed your query parameters using the
-`embeddedBy` field. Only string-typed
-parameters can be embedded:
+`embeddedBy` field. Only string-typed parameters can be embedded:
 
 ```yaml
 tools:
@@ -61,10 +79,13 @@ tools:
     parameters:
       - name: content
         type: string
+        description: The raw text content to be stored in the database.
       - name: vector_string
         type: string
-        description: The text to be vectorized and stored.
-        embeddedBy: gemini-model # refers to the name of a defined embedding model
+        # This parameter is hidden from the LLM.
+        # It automatically copies the value from 'content' and embeds it.
+        valueFromParam: content
+        embeddedBy: gemini-model
 
   # Semantic search tool
   search_embedding:

internal/server/config.go

@@ -296,6 +296,43 @@ func (c *ToolConfigs) UnmarshalYAML(ctx context.Context, unmarshal func(interfac
 			return fmt.Errorf("invalid 'kind' field for tool %q (must be a string)", name)
 		}
 
+		// validify parameter references
+		if rawParams, ok := v["parameters"]; ok {
+			if paramsList, ok := rawParams.([]any); ok {
+				// Turn params into a map
+				validParamNames := make(map[string]bool)
+				for _, rawP := range paramsList {
+					if pMap, ok := rawP.(map[string]any); ok {
+						if pName, ok := pMap["name"].(string); ok && pName != "" {
+							validParamNames[pName] = true
+						}
+					}
+				}
+
+				// Validate references
+				for i, rawP := range paramsList {
+					pMap, ok := rawP.(map[string]any)
+					if !ok {
+						continue
+					}
+
+					pName, _ := pMap["name"].(string)
+					refName, _ := pMap["valueFromParam"].(string)
+
+					if refName != "" {
+						// Check if the referenced parameter exists
+						if !validParamNames[refName] {
+							return fmt.Errorf("tool %q config error: parameter %q (index %d) references '%q' in the 'valueFromParam' field, which is not a defined parameter", name, pName, i, refName)
+						}
+
+						// Check for self-reference
+						if refName == pName {
+							return fmt.Errorf("tool %q config error: parameter %q cannot copy value from itself", name, pName)
+						}
+					}
+				}
+			}
+		}
 		yamlDecoder, err := util.NewStrictDecoder(v)
 		if err != nil {
 			return fmt.Errorf("error creating YAML decoder for tool %q: %w", name, err)

internal/util/parameters/parameters.go

@@ -134,7 +134,12 @@ func ParseParams(ps Parameters, data map[string]any, claimsMap map[string]map[st
 		var err error
 		paramAuthServices := p.GetAuthServices()
 		name := p.GetName()
-		if len(paramAuthServices) == 0 {
+
+		sourceParamName := p.GetValueFromParam()
+		if sourceParamName != "" {
+			v = data[sourceParamName]
+
+		} else if len(paramAuthServices) == 0 {
 			// parse non auth-required parameter
 			var ok bool
 			v, ok = data[name]
@@ -318,6 +323,7 @@ type Parameter interface {
 	GetRequired() bool
 	GetAuthServices() []ParamAuthService
 	GetEmbeddedBy() string
+	GetValueFromParam() string
 	Parse(any) (any, error)
 	Manifest() ParameterManifest
 	McpManifest() (ParameterMcpManifest, []string)
@@ -465,6 +471,9 @@ func ParseParameter(ctx context.Context, p map[string]any, paramType string) (Pa
 func (ps Parameters) Manifest() []ParameterManifest {
 	rtn := make([]ParameterManifest, 0, len(ps))
 	for _, p := range ps {
+		if p.GetValueFromParam() != "" {
+			continue
+		}
 		rtn = append(rtn, p.Manifest())
 	}
 	return rtn
@@ -476,6 +485,11 @@ func (ps Parameters) McpManifest() (McpToolsSchema, map[string][]string) {
 	authParam := make(map[string][]string)
 
 	for _, p := range ps {
+		// If the parameter is sourced from another param, skip it in the MCP manifest
+		if p.GetValueFromParam() != "" {
+			continue
+		}
+
 		name := p.GetName()
 		paramManifest, authParamList := p.McpManifest()
 		defaultV := p.GetDefault()
@@ -509,6 +523,7 @@ type ParameterManifest struct {
 	Default              any                `json:"default,omitempty"`
 	AdditionalProperties any                `json:"additionalProperties,omitempty"`
 	EmbeddedBy           string             `json:"embeddedBy,omitempty"`
+	ValueFromParam       string             `json:"valueFromParam,omitempty"`
 }
 
 // ParameterMcpManifest represents properties when served as part of a ToolMcpManifest.
@@ -531,6 +546,7 @@ type CommonParameter struct {
 	AuthServices   []ParamAuthService `yaml:"authServices"`
 	AuthSources    []ParamAuthService `yaml:"authSources"` // Deprecated: Kept for compatibility.
 	EmbeddedBy     string             `yaml:"embeddedBy"`
+	ValueFromParam string             `yaml:"valueFromParam"`
 }
 
 // GetName returns the name specified for the Parameter.
@@ -588,10 +604,16 @@ func (p *CommonParameter) IsExcludedValues(v any) bool {
 	return false
 }
 
+// GetEmbeddedBy returns the embedding model name for the Parameter.
 func (p *CommonParameter) GetEmbeddedBy() string {
 	return p.EmbeddedBy
 }
 
+// GetValueFromParam returns the param value to copy from.
+func (p *CommonParameter) GetValueFromParam() string {
+	return p.ValueFromParam
+}
+
 // MatchStringOrRegex checks if the input matches the target
 func MatchStringOrRegex(input, target any) bool {
 	targetS, ok := target.(string)

tests/embedding.go

@@ -64,10 +64,11 @@ func AddSemanticSearchConfig(t *testing.T, config map[string]any, toolKind, inse
 				"description": "The text content associated with the vector.",
 			},
 			map[string]any{
-				"name":        "text_to_embed",
-				"type":        "string",
-				"description": "The text content used to generate the vector.",
-				"embeddedBy":  "gemini_model",
+				"name":           "text_to_embed",
+				"type":           "string",
+				"description":    "The text content used to generate the vector.",
+				"embeddedBy":     "gemini_model",
+				"valueFromParam": "content",
 			},
 		},
 	}
@@ -108,7 +109,7 @@ func RunSemanticSearchToolInvokeTest(t *testing.T, insertWant, mcpInsertWant, se
 			name:        "HTTP invoke insert_docs",
 			api:         "http://127.0.0.1:5000/api/tool/insert_docs/invoke",
 			isMcp:       false,
-			requestBody: `{"content": "The quick brown fox jumps over the lazy dog", "text_to_embed": "The quick brown fox jumps over the lazy dog"}`,
+			requestBody: `{"content": "The quick brown fox jumps over the lazy dog"}`,
 			want:        insertWant,
 		},
 		{
@@ -131,8 +132,7 @@ func RunSemanticSearchToolInvokeTest(t *testing.T, insertWant, mcpInsertWant, se
 				Params: map[string]any{
 					"name": "insert_docs",
 					"arguments": map[string]any{
-						"content":       "The quick brown fox jumps over the lazy dog",
-						"text_to_embed": "The quick brown fox jumps over the lazy dog",
+						"content": "The quick brown fox jumps over the lazy dog",
 					},
 				},
 			},