--- title: "9. Tools" description: "MCP Description specification v0.7.0 — 9. Tools." source: "https://mcpdesc.org/docs/specification/0.7.0/tools/" --- Mirrored specification This page mirrors **9\. Tools** of the MCP Description specification **v0.7.0**. The canonical source of truth is [cisco-open/mcptoolkit-contract](https://github.com/cisco-open/mcptoolkit-contract/blob/main/spec/sections/09-tools.md). Where this page differs from upstream, upstream wins. ## 9\. Tools The `tools` array declares the tools exposed by the MCP server. Each tool represents a server-side function that clients can invoke. ### 9.1 Tool Object | Property | Type | Required | Description | | ------------ | ----------------------------------------------- | -------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | name | string | **Yes** | Programmatic tool name (identifier). | | title | string | No | Human-readable display name for UI contexts. Since MCP 2025-06-18. | | description | string | No | Human-readable tool description. | | inputSchema | object | No | JSON Schema for tool input parameters. | | outputSchema | object | No | JSON Schema for structured tool output. Since MCP 2025-06-18. | | annotations | [Tool Annotations Object](#93-tool-annotations) | No | Behavioral hints. Since MCP 2025-03-26. | | execution | [Execution Object](#94-execution-object) | No | Execution properties. Since MCP 2025-11-25. | | icons | array | No | Icons for UI display. Since MCP 2025-11-25. | | tags | array | No | Categorization tags. When a root-level tags array is present, values MUST reference declared tag names (see [Section 12.3](/docs/specification/0.7.0/tags#123-tag-references)). | | deprecated | boolean | No | Whether the tool is deprecated. | | \_meta | object | No | Protocol-reserved metadata. Since MCP 2025-06-18. | ### 9.2 Input and Output Schemas The `inputSchema` property, when present, MUST be a valid JSON Schema object describing the tool’s input parameters. It typically has `"type": "object"` with `properties` and `required` fields. The `outputSchema` property, when present, MUST be a valid JSON Schema object describing the tool’s structured output. It defaults to JSON Schema 2020-12 dialect when no explicit `$schema` is provided. Both schemas MAY include an explicit `$schema` property to declare the JSON Schema dialect (since MCP 2025-11-25). ### 9.3 Tool Annotations Tool annotations provide hints about tool behavior. These are advisory — implementations MUST NOT rely on annotations being accurate. | Property | Type | Default | Description | | --------------- | ------- | ------- | ------------------------------------------------------------ | | title | string | — | Human-readable title for the tool | | readOnlyHint | boolean | false | Tool does not modify its environment | | destructiveHint | boolean | true | Tool may perform destructive updates | | idempotentHint | boolean | false | Repeated calls with same arguments have no additional effect | | openWorldHint | boolean | true | Tool may interact with external entities | The annotations object allows additional properties for forward compatibility. ### 9.4 Execution Object | Property | Type | Default | Description | | ----------- | ------ | ----------- | ------------------------------------------------------------------------------------------ | | taskSupport | string | "forbidden" | Whether the tool supports task-augmented execution: "forbidden", "optional", or "required" | ### 9.5 Example ```json { "tools": [ { "name": "analyze_game", "title": "Analyze Chess Game", "description": "Analyze a chess game from PGN notation and return evaluation scores", "inputSchema": { "type": "object", "properties": { "pgn": { "type": "string", "description": "Game in Portable Game Notation (PGN) format" }, "depth": { "type": "integer", "description": "Analysis depth in half-moves", "minimum": 1, "maximum": 40 } }, "required": ["pgn"] }, "outputSchema": { "type": "object", "properties": { "evaluation": { "type": "number", "description": "Centipawn evaluation" }, "best_move": { "type": "string", "description": "Best move in algebraic notation" }, "blunders": { "type": "array", "items": { "type": "object", "properties": { "move_number": { "type": "integer" }, "move": { "type": "string" }, "evaluation_loss": { "type": "number" } } } } } }, "annotations": { "readOnlyHint": true, "destructiveHint": false, "idempotentHint": true }, "tags": ["analysis", "chess"] }, { "name": "get_player_rating", "title": "Get Player Rating", "description": "Get the current Elo rating and rating history for a chess player", "inputSchema": { "type": "object", "properties": { "player_id": { "type": "string", "description": "Unique player identifier" }, "rating_type": { "type": "string", "enum": ["classical", "rapid", "blitz", "bullet"], "description": "Type of rating to retrieve" } }, "required": ["player_id"] }, "annotations": { "readOnlyHint": true, "destructiveHint": false }, "tags": ["rating", "player"] }, { "name": "record_game_result", "title": "Record Game Result", "description": "Record the result of a chess game and update player ratings", "inputSchema": { "type": "object", "properties": { "white_player_id": { "type": "string", "description": "White player identifier" }, "black_player_id": { "type": "string", "description": "Black player identifier" }, "result": { "type": "string", "enum": ["1-0", "0-1", "1/2-1/2"], "description": "Game result in standard notation" }, "pgn": { "type": "string", "description": "Full game PGN (optional)" }, "time_control": { "type": "string", "description": "Time control (e.g., '10+0', '3+2')" } }, "required": ["white_player_id", "black_player_id", "result"] }, "annotations": { "readOnlyHint": false, "destructiveHint": false, "idempotentHint": false }, "tags": ["rating", "game"] } ] } ```