MCP Toolbox for Databases

--- title: "Tools" type: docs weight: 2 description: > Tools define actions an agent can take -- such as reading and writing to a source. --- A tool represents an action your agent can take, such as running a SQL statement. You can define Tools as a map in the `tools` section of your `tools.yaml` file. Typically, a tool will require a source to act on: ```yaml tools: search_flights_by_number: kind: postgres-sql source: my-pg-instance statement: | SELECT * FROM flights WHERE airline = $1 AND flight_number = $2 LIMIT 10 description: | Use this tool to get information for a specific flight. Takes an airline code and flight number and returns info on the flight. Do NOT use this tool with a flight id. Do NOT guess an airline code or flight number. An airline code is a code for an airline service consisting of a two-character airline designator and followed by a flight number, which is a 1 to 4 digit number. For example, if given CY 0123, the airline is "CY", and flight_number is "123". Another example for this is DL 1234, the airline is "DL", and flight_number is "1234". If the tool returns more than one option choose the date closest to today. Example: {{ "airline": "CY", "flight_number": "888", }} Example: {{ "airline": "DL", "flight_number": "1234", }} parameters: - name: airline type: string description: Airline unique 2 letter identifier - name: flight_number type: string description: 1 to 4 digit number ``` ## Specifying Parameters Parameters for each Tool will define what inputs the agent will need to provide to invoke them. Parameters should be pass as a list of Parameter objects: ```yaml parameters: - name: airline type: string description: Airline unique 2 letter identifier - name: flight_number type: string description: 1 to 4 digit number ``` ### Basic Parameters Basic parameters types include `string`, `integer`, `float`, `boolean` types. In most cases, the description will be provided to the LLM as context on specifying the parameter. ```yaml parameters: - name: airline type: string description: Airline unique 2 letter identifier ``` | **field** | **type** | **required** | **description** | |-------------|:---------------:|:------------:|-----------------------------------------------------------------------------| | name | string | true | Name of the parameter. | | type | string | true | Must be one of "string", "integer", "float", "boolean" "array" | | description | string | true | Natural language description of the parameter to describe it to the agent. | | default | parameter type | false | Default value of the parameter. If provided, `required` will be `false`. | | required | bool | false | Indicate if the parameter is required. Default to `true`. | ### Array Parameters The `array` type is a list of items passed in as a single parameter. To use the `array` type, you must also specify what kind of items are in the list using the items field: ```yaml parameters: - name: preferred_airlines type: array description: A list of airline, ordered by preference. items: name: name type: string description: Name of the airline. statement: | SELECT * FROM airlines WHERE preferred_airlines = ANY($1); ``` | **field** | **type** | **required** | **description** | |-------------|:----------------:|:------------:|-----------------------------------------------------------------------------| | name | string | true | Name of the parameter. | | type | string | true | Must be "array" | | description | string | true | Natural language description of the parameter to describe it to the agent. | | default | parameter type | false | Default value of the parameter. If provided, `required` will be `false`. | | required | bool | false | Indicate if the parameter is required. Default to `true`. | | items | parameter object | true | Specify a Parameter object for the type of the values in the array. | {{< notice note >}} Items in array should not have a `default` or `required` value. If provided, it will be ignored. {{< /notice >}} ### Map Parameters The map type is a collection of key-value pairs. It can be configured in two ways: - Generic Map: By default, it accepts values of any primitive type (string, integer, float, boolean), allowing for mixed data. - Typed Map: By setting the valueType field, you can enforce that all values within the map must be of the same specified type. #### Generic Map (Mixed Value Types) This is the default behavior when valueType is omitted. It's useful for passing a flexible group of settings. ```yaml parameters: - name: execution_context type: map description: A flexible set of key-value pairs for the execution environment. ``` #### Typed Map Specify valueType to ensure all values in the map are of the same type. An error will be thrown in case of value type mismatch. ```yaml parameters: - name: user_scores type: map description: A map of user IDs to their scores. All scores must be integers. valueType: integer # This enforces the value type for all entries. ``` ### Authenticated Parameters Authenticated parameters are automatically populated with user information decoded from [ID tokens](../authServices/#specifying-id-tokens-from-clients) that are passed in request headers. They do not take input values in request bodies like other parameters. To use authenticated parameters, you must configure the tool to map the required [authServices](../authServices/) to specific claims within the user's ID token. ```yaml tools: search_flights_by_user_id: kind: postgres-sql source: my-pg-instance statement: | SELECT * FROM flights WHERE user_id = $1 parameters: - name: user_id type: string description: Auto-populated from Google login authServices: # Refer to one of the `authServices` defined - name: my-google-auth # `sub` is the OIDC claim field for user ID field: sub ``` | **field** | **type** | **required** | **description** | |-----------|:--------:|:------------:|-----------------------------------------------------------------------------------------| | name | string | true | Name of the [authServices](../authServices/) used to verify the OIDC auth token. | | field | string | true | Claim field decoded from the OIDC token used to auto-populate this parameter. | ### Template Parameters Template parameters types include `string`, `integer`, `float`, `boolean` types. In most cases, the description will be provided to the LLM as context on specifying the parameter. Template parameters will be inserted into the SQL statement before executing the prepared statement. They will be inserted without quotes, so to insert a string using template parameters, quotes must be explicitly added within the string. Template parameter arrays can also be used similarly to basic parameters, and array items must be strings. Once inserted into the SQL statement, the outer layer of quotes will be removed. Therefore to insert strings into the SQL statement, a set of quotes must be explicitly added within the string. {{< notice warning >}} Because template parameters can directly replace identifiers, column names, and table names, they are prone to SQL injections. Basic parameters are preferred for performance and safety reasons. {{< /notice >}} ```yaml tools: select_columns_from_table: kind: postgres-sql source: my-pg-instance statement: | SELECT {{array .columnNames}} FROM {{.tableName}} description: | Use this tool to list all information from a specific table. Example: {{ "tableName": "flights", "columnNames": ["id", "name"] }} templateParameters: - name: tableName type: string description: Table to select from - name: columnNames type: array description: The columns to select items: name: column type: string description: Name of a column to select ``` | **field** | **type** | **required** | **description** | |-------------|:----------------:|:-------------:|-------------------------------------------------------------------------------------| | name | string | true | Name of the template parameter. | | type | string | true | Must be one of "string", "integer", "float", "boolean" "array" | | description | string | true | Natural language description of the template parameter to describe it to the agent. | | items | parameter object |true (if array)| Specify a Parameter object for the type of the values in the array (string only). | ## Authorized Invocations You can require an authorization check for any Tool invocation request by specifying an `authRequired` field. Specify a list of [authServices](../authServices/) defined in the previous section. ```yaml tools: search_all_flight: kind: postgres-sql source: my-pg-instance statement: | SELECT * FROM flights # A list of `authServices` defined previously authRequired: - my-google-auth - other-auth-service ``` ## Kinds of tools