fix(looker): Convert prebuilt tool yaml to flat format (googleapis#3022)

## Description

Migrated the prebuilt tool files to use the flat format, then did some
hand editing.
Checked using Gemini CLI that the same output is delivered to the MCP
client.

Also fixed up some of the docs to use the flat format.

## PR Checklist

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- [x] Make sure you reviewed

[CONTRIBUTING.md](https://github.com/googleapis/mcp-toolbox/blob/main/CONTRIBUTING.md)
- [x] Make sure to open an issue as a

[bug/issue](https://github.com/googleapis/mcp-toolbox/issues/new/choose)
  before writing your code! That way we can discuss the change, evaluate
  designs, and agree on the general idea
- [x] Ensure the tests and linter pass
- [x] Code coverage does not decrease (if any source code was changed)
- [x] Appropriate docs were updated (if necessary)
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Author: drstrangelooker

docs/en/integrations/looker/source.md

@@ -63,17 +63,37 @@ To initialize the application default credential run `gcloud auth login
 
 ## Example
 
+Initialize a Looker source for standard and development tools:
+
 ```yaml
 kind: source
 name: my-looker-source
 type: looker
-base_url: http://looker.example.com
-client_id: ${LOOKER_CLIENT_ID}
-client_secret: ${LOOKER_CLIENT_SECRET}
-project: ${LOOKER_PROJECT}
-location: ${LOOKER_LOCATION}
-verify_ssl: true
+base_url: ${LOOKER_BASE_URL}
+client_id: ${LOOKER_CLIENT_ID:}
+client_secret: ${LOOKER_CLIENT_SECRET:}
+verify_ssl: ${LOOKER_VERIFY_SSL:true}
+timeout: 600s
+use_client_oauth: ${LOOKER_USE_CLIENT_OAUTH:false}
+show_hidden_models: ${LOOKER_SHOW_HIDDEN_MODELS:true}
+show_hidden_explores: ${LOOKER_SHOW_HIDDEN_EXPLORES:true}
+show_hidden_fields: ${LOOKER_SHOW_HIDDEN_FIELDS:true}
+```
+
+Initialize a Looker source for conversational analytics:
+
+```yaml
+kind: source
+name: my-looker-conversational-source
+type: looker
+base_url: ${LOOKER_BASE_URL}
+client_id: ${LOOKER_CLIENT_ID:}
+client_secret: ${LOOKER_CLIENT_SECRET:}
+verify_ssl: ${LOOKER_VERIFY_SSL:true}
 timeout: 600s
+use_client_oauth: ${LOOKER_USE_CLIENT_OAUTH:false}
+project: ${LOOKER_PROJECT:}
+location: ${LOOKER_LOCATION:}
 ```
 
 The Looker base url will look like "https://looker.example.com", don't include

docs/en/integrations/looker/tools/looker-validate-project.md

@@ -19,27 +19,27 @@ A "looker-validate-project" tool checks the syntax of a LookML project and repor
 ## Example
 
 ```yaml
-tools:
-    validate_project:
-        kind: looker-validate-project
-        source: looker-source
-        description: |
-          This tool checks a LookML project for syntax errors.
+kind: tool
+name: validate_project
+type: looker-validate-project
+source: looker-source
+description: |
+  This tool checks a LookML project for syntax errors.
 
-          Prerequisite: The Looker session must be in Development Mode. Use `dev_mode: true` first.
+  Prerequisite: The Looker session must be in Development Mode. Use `dev_mode: true` first.
 
-          Parameters:
-          - project_id (required): The unique ID of the LookML project.
+  Parameters:
+  - project_id (required): The unique ID of the LookML project.
 
-          Output:
-          A list of error details including the file path and line number, and also a list of models
-          that are not currently valid due to LookML errors.
+  Output:
+  A list of error details including the file path and line number, and also a list of models
+  that are not currently valid due to LookML errors.
 ```
 
 ## Reference
 
 | **field**   | **type** | **required** | **description**                                    |
 |-------------|:--------:|:------------:|----------------------------------------------------|
-| kind        |  string  |     true     | Must be "looker-validate-project".                 |
+| type        |  string  |     true     | Must be "looker-validate-project".                 |
 | source      |  string  |     true     | Name of the source Looker instance.                |
 | description |  string  |     true     | Description of the tool that is passed to the LLM. |

internal/prebuiltconfigs/tools/looker-conversational-analytics.yaml

@@ -1,4 +1,4 @@
-# Copyright 2025 Google LLC
+# Copyright 2026 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -12,57 +12,60 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-sources:
-    looker-source:
-        kind: looker
-        base_url: ${LOOKER_BASE_URL}
-        client_id: ${LOOKER_CLIENT_ID:}
-        client_secret: ${LOOKER_CLIENT_SECRET:}
-        verify_ssl: ${LOOKER_VERIFY_SSL:true}
-        timeout: 600s
-        use_client_oauth: ${LOOKER_USE_CLIENT_OAUTH:false}
-        project: ${LOOKER_PROJECT:}
-        location: ${LOOKER_LOCATION:}
+kind: source
+name: looker-source
+type: looker
+base_url: ${LOOKER_BASE_URL}
+client_id: ${LOOKER_CLIENT_ID:}
+client_secret: ${LOOKER_CLIENT_SECRET:}
+verify_ssl: ${LOOKER_VERIFY_SSL:true}
+timeout: 600s
+use_client_oauth: ${LOOKER_USE_CLIENT_OAUTH:false}
+project: ${LOOKER_PROJECT:}
+location: ${LOOKER_LOCATION:}
+---
+kind: tool
+name: ask_data_insights
+type: looker-conversational-analytics
+source: looker-source
+description: |
+  Use this tool to ask questions about your data using the Looker Conversational
+  Analytics API. You must provide a natural language query and a list of
+  1 to 5 model and explore combinations (e.g. [{'model': 'the_model', 'explore': 'the_explore'}]).
+  Use the 'get_models' and 'get_explores' tools to discover available models and explores.
+---
+kind: tool
+name: get_models
+type: looker-get-models
+source: looker-source
+description: |
+  get_models Tool
+  
+  This tool retrieves a list of available LookML models in the Looker instance.
+  LookML models define the data structure and relationships that users can query.
+  The output includes details like the model's `name` and `label`, which are
+  essential for subsequent calls to tools like `get_explores` or `query`.
+  
+  This tool takes no parameters.
+---
+kind: tool
+name: get_explores
+type: looker-get-explores
+source: looker-source
+description: |
+  get_explores Tool
 
-tools:
-    ask_data_insights:
-        kind: looker-conversational-analytics
-        source: looker-source
-        description: |
-          Use this tool to ask questions about your data using the Looker Conversational
-          Analytics API. You must provide a natural language query and a list of
-          1 to 5 model and explore combinations (e.g. [{'model': 'the_model', 'explore': 'the_explore'}]).
-          Use the 'get_models' and 'get_explores' tools to discover available models and explores.
-
-    get_models:
-        kind: looker-get-models
-        source: looker-source
-        description: |
-          get_models Tool
-
-          This tool retrieves a list of available LookML models in the Looker instance.
-          LookML models define the data structure and relationships that users can query.
-          The output includes details like the model's `name` and `label`, which are
-          essential for subsequent calls to tools like `get_explores` or `query`.
-
-          This tool takes no parameters.
+  This tool retrieves a list of explores defined within a specific LookML model.
+  Explores represent a curated view of your data, typically joining several
+  tables together to allow for focused analysis on a particular subject area.
+  The output provides details like the explore's `name` and `label`.
 
-    get_explores:
-        kind: looker-get-explores
-        source: looker-source
-        description: |
-          get_explores Tool
-
-          This tool retrieves a list of explores defined within a specific LookML model.
-          Explores represent a curated view of your data, typically joining several
-          tables together to allow for focused analysis on a particular subject area.
-          The output provides details like the explore's `name` and `label`.
-
-          Parameters:
-          - model_name (required): The name of the LookML model, obtained from `get_models`.
-
-toolsets:
-    looker_conversational_analytics_tools:
-        - ask_data_insights
-        - get_models
-        - get_explores
+  Parameters:
+  - model_name (required): The name of the LookML model, obtained from `get_models`.
+---
+kind: toolset
+name: looker_conversational_analytics_tools
+tools:
+- ask_data_insights
+- get_models
+- get_explores