Struct ToolMetadata 

pub struct ToolMetadata {
    pub name: String,
    pub title: Option<String>,
    pub description: Option<String>,
    pub parameters: Value,
    pub output_schema: Option<Value>,
    pub method: String,
    pub path: String,
    pub security: Option<Vec<String>>,
    pub parameter_mappings: HashMap<String, ParameterMapping>,
}

Internal metadata for tools generated from OpenAPI operations.

This struct contains all the information needed to execute HTTP requests and is used internally by the OpenAPI server. It includes fields that are not part of the MCP specification but are necessary for HTTP execution.

For MCP compliance, this struct is converted to rmcp::model::Tool using the From trait implementation, which only includes MCP-compliant fields.

MCP Tool Annotations

When converted to MCP tools, this metadata automatically generates appropriate annotation hints based on HTTP method semantics (see ToolMetadata::generate_annotations). These annotations help MCP clients understand the nature of each tool operation.

Fields

name: String

Tool name - exposed to MCP clients

title: Option<String>

Tool title - human-readable display name exposed to MCP clients

description: Option<String>

Tool description - exposed to MCP clients

parameters: Value

Input parameters schema - exposed to MCP clients as inputSchema

output_schema: Option<Value>

Output schema - exposed to MCP clients as outputSchema

method: String

HTTP method (GET, POST, etc.) - internal only, not exposed to MCP

path: String

URL path for the API endpoint - internal only, not exposed to MCP

security: Option<Vec<String>>

Security requirements from OpenAPI spec - internal only, not exposed to MCP

parameter_mappings: HashMap<String, ParameterMapping>

Parameter mappings for converting between MCP and OpenAPI parameters - internal only, not exposed to MCP

Implementations

impl ToolMetadata

pub fn requires_auth(&self) -> bool

Check if this tool requires authentication based on OpenAPI security definitions

pub fn generate_annotations(&self) -> Option<ToolAnnotations>

Generate MCP annotations based on HTTP method semantics.

This method maps HTTP verbs to appropriate MCP tool annotation hints following the semantics defined in RFC 9110 (HTTP Semantics) and the Model Context Protocol specification.

HTTP Method to Annotation Mapping

• GET, HEAD, OPTIONS: Safe, idempotent read operations

  • readOnlyHint: true - No state modification
  • destructiveHint: false - Doesn’t alter existing resources
  • idempotentHint: true - Multiple requests have same effect
  • openWorldHint: true - Interacts with external HTTP API

• POST: Creates resources; not idempotent, not destructive

  • readOnlyHint: false - Modifies state
  • destructiveHint: false - Creates new resources (doesn’t destroy existing)
  • idempotentHint: false - Multiple requests may create multiple resources
  • openWorldHint: true - Interacts with external HTTP API

• PUT: Replaces/updates resources; idempotent but destructive

  • readOnlyHint: false - Modifies state
  • destructiveHint: true - Replaces existing resource state
  • idempotentHint: true - Multiple identical requests have same effect
  • openWorldHint: true - Interacts with external HTTP API

• PATCH: Modifies resources; destructive and typically not idempotent

  • readOnlyHint: false - Modifies state
  • destructiveHint: true - Alters existing resource state
  • idempotentHint: false - Effect may vary based on current state
  • openWorldHint: true - Interacts with external HTTP API

• DELETE: Removes resources; idempotent but destructive

  • readOnlyHint: false - Modifies state
  • destructiveHint: true - Removes resources
  • idempotentHint: true - Multiple deletions are no-ops after first
  • openWorldHint: true - Interacts with external HTTP API

Returns

• Some(ToolAnnotations) for recognized HTTP methods (GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS)
• None for unknown or unsupported HTTP methods

Notes

• HTTP method comparison is case-insensitive
• The title field in annotations is always None (title is handled via Tool.title)
• openWorldHint is always true since all OpenAPI tools interact with external HTTP APIs

Trait Implementations

impl Clone for ToolMetadata

fn clone(&self) -> ToolMetadata

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ToolMetadata

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl From<&ToolMetadata> for Tool

Converts internal ToolMetadata to MCP-compliant Tool.

This implementation ensures that only MCP-compliant fields are exposed to clients. Internal fields like method and path are not included in the conversion.

fn from(metadata: &ToolMetadata) -> Self

Converts to this type from the input type.

impl Serialize for ToolMetadata

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.