fix: add items to parameter manifest (#293)

`items` are not specified in the manifest for parameters, which means
the client doesn't parse them correctly when presented to the LLMs. This
PR adds `items` as part of manifest.

Example manifest:
```
{
    "serverVersion": "0.1.0",
    "tools": {
        "tool_name": {
            "description": "description of the tool...",
            "parameters": [{
                "name": "foos",
                "type": "array",
                "description": "A list of foo.",
                "authSources": [],
                "items": {"name": "foo", "type": "string", "description": "foobar.", "authSources": []}
            }]
        }
    }
}
```

Fixes #292 🦕

internal/tools/parameters.go

@@ -234,11 +234,11 @@ func (ps Parameters) Manifest() []ParameterManifest {
 
 // ParameterManifest represents parameters when served as part of a ToolManifest.
 type ParameterManifest struct {
-	Name        string   `json:"name"`
-	Type        string   `json:"type"`
-	Description string   `json:"description"`
-	AuthSources []string `json:"authSources"`
-	// Parameter   *ParameterManifest `json:"parameter,omitempty"`
+	Name        string             `json:"name"`
+	Type        string             `json:"type"`
+	Description string             `json:"description"`
+	AuthSources []string           `json:"authSources"`
+	Items       *ParameterManifest `json:"items,omitempty"`
 }
 
 // CommonParameter are default fields that are emebdding in most Parameter implementations. Embedding this stuct will give the object Name() and Type() functions.
@@ -259,7 +259,7 @@ func (p *CommonParameter) GetType() string {
 	return p.Type
 }
 
-// GetType returns the type specified for the Parameter.
+// Manifest returns the manifest for the Parameter.
 func (p *CommonParameter) Manifest() ParameterManifest {
 	// only list ParamAuthSource names (without fields) in manifest
 	authNames := make([]string, len(p.AuthSources))
@@ -560,3 +560,20 @@ func (p *ArrayParameter) Parse(v any) (any, error) {
 func (p *ArrayParameter) GetAuthSources() []ParamAuthSource {
 	return p.AuthSources
 }
+
+// Manifest returns the manifest for the ArrayParameter.
+func (p *ArrayParameter) Manifest() ParameterManifest {
+	// only list ParamAuthSource names (without fields) in manifest
+	authNames := make([]string, len(p.AuthSources))
+	for i, a := range p.AuthSources {
+		authNames[i] = a.Name
+	}
+	items := p.Items.Manifest()
+	return ParameterManifest{
+		Name:        p.Name,
+		Type:        p.Type,
+		Description: p.Desc,
+		AuthSources: authNames,
+		Items:       &items,
+	}
+}

internal/tools/parameters_test.go

@@ -661,3 +661,51 @@ func TestParamValues(t *testing.T) {
 		})
 	}
 }
+
+func TestParamManifest(t *testing.T) {
+	tcs := []struct {
+		name string
+		in   tools.Parameter
+		want tools.ParameterManifest
+	}{
+		{
+			name: "string",
+			in:   tools.NewStringParameter("foo-string", "bar"),
+			want: tools.ParameterManifest{Name: "foo-string", Type: "string", Description: "bar", AuthSources: []string{}},
+		},
+		{
+			name: "int",
+			in:   tools.NewIntParameter("foo-int", "bar"),
+			want: tools.ParameterManifest{Name: "foo-int", Type: "integer", Description: "bar", AuthSources: []string{}},
+		},
+		{
+			name: "float",
+			in:   tools.NewFloatParameter("foo-float", "bar"),
+			want: tools.ParameterManifest{Name: "foo-float", Type: "float", Description: "bar", AuthSources: []string{}},
+		},
+		{
+			name: "boolean",
+			in:   tools.NewBooleanParameter("foo-bool", "bar"),
+			want: tools.ParameterManifest{Name: "foo-bool", Type: "boolean", Description: "bar", AuthSources: []string{}},
+		},
+		{
+			name: "array",
+			in:   tools.NewArrayParameter("foo-array", "bar", tools.NewStringParameter("foo-string", "bar")),
+			want: tools.ParameterManifest{
+				Name:        "foo-array",
+				Type:        "array",
+				Description: "bar",
+				AuthSources: []string{},
+				Items:       &tools.ParameterManifest{Name: "foo-string", Type: "string", Description: "bar", AuthSources: []string{}},
+			},
+		},
+	}
+	for _, tc := range tcs {
+		t.Run(tc.name, func(t *testing.T) {
+			got := tc.in.Manifest()
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Fatalf("unexpected manifest: got %+v, want %+v", got, tc.want)
+			}
+		})
+	}
+}