[Agent Builder] Add page about models (elastic#3338)

closes elastic/search-team#10745
closes elastic/docs-content-internal#364

Author: leemthompo

solutions/search/agent-builder/get-started.md

@@ -88,6 +88,12 @@ Learn more in [Agent Chat](chat.md).
 
 ::::
 
+::::{step} Configure model (optional)
+
+By default, {{agent-builder}} uses the Elastic Managed LLM. To use a different model, refer to [model selection and configuration](models.md).
+
+::::
+
 ::::{step} Begin building agents and tools
 
 Once you've tested the default **Elastic AI Agent** with the [built-in Elastic tools](tools.md), you can begin [building your own agents](agent-builder-agents.md#create-a-new-agent) with custom instructions and [creating your own tools](tools.md#create-custom-tools) to assign them.

solutions/search/agent-builder/limitations-known-issues.md

@@ -20,17 +20,11 @@ These pages are currently hidden from the docs TOC and have `noindexed` meta hea
 
 {{agent-builder}} must be enabled for non-serverless deployments {applies_to}`stack: preview 9.2`. Refer to [Get started](get-started.md#enable-agent-builder) for instructions.
 
-### Model selection
-
-Initially, {{agent-builder}} only supports working with the [Elastic Managed LLM](kibana://reference/connectors-kibana/elastic-managed-llm.md) running on the [Elastic Inference Service](/explore-analyze/elastic-inference/eis.md) {applies_to}`stack: preview 9.2`.
-
-Learn about [pricing](https://www.elastic.co/pricing/serverless-search) for the Elastic Managed LLM.
-
 ## Known issues
 
 ### Incompatible LLMs
 
-While Elastic offers LLM [connectors](kibana://reference/connectors-kibana.md) for many different vendors and models, not all LLMs are robust enough to be used with {{agent-builder}}. We recommend using the [Elastic Managed LLM](kibana://reference/connectors-kibana/elastic-managed-llm.md) (the default).
+While Elastic offers LLM [connectors](kibana://reference/connectors-kibana.md) for many different vendors and models, not all LLMs are robust enough to be used with {{agent-builder}}. We recommend using the [Elastic Managed LLM](kibana://reference/connectors-kibana/elastic-managed-llm.md) (the default). Learn more in [](models.md).
 
 The following errors suggest your selected model may not be compatible with {{agent-builder}}:
 
@@ -69,4 +63,4 @@ This results in parsing errors like this:
 ]
 ```
 
-    
+    

solutions/search/agent-builder/models.md

@@ -12,4 +12,87 @@ These pages are currently hidden from the docs TOC and have `noindexed` meta hea
 **Go to the docs [landing page](/solutions/search/elastic-agent-builder.md).**
 :::
 
-# Using different models in {{agent-builder}}
+# Using different models in {{agent-builder}}
+
+{{agent-builder}} uses large language models (LLMs) to power agent reasoning and decision-making. By default, agents use the Elastic Managed LLM, but you can configure other models through Kibana connectors.
+
+## Default model configuration
+
+By default, {{agent-builder}} uses the Elastic Managed LLM connector running on the [Elastic Inference Service](/explore-analyze/elastic-inference/eis.md) {applies_to}`serverless: preview` {applies_to}`ess: preview 9.2`. 
+
+This managed service requires zero setup and no additional API key management.
+
+Learn more about the [Elastic Managed LLM connector](kibana://reference/connectors-kibana/elastic-managed-llm.md) and [pricing](https://www.elastic.co/pricing).
+
+## Change the default model
+
+By default, {{agent-builder}} uses the Elastic Managed LLM. To use a different model, select a configured connector and set it as the default.
+
+### Use a pre-configured connector
+
+1. Search for **GenAI Settings** in the global search field
+2. Select your preferred connector from the **Default AI Connector** dropdown
+3. Save your changes
+
+### Create a new connector in the UI
+
+1. Find connectors under **Alerts and Insights / Connectors** in the [global search bar](/explore-analyze/find-and-organize/find-apps-and-objects.md)
+2. Select **Create Connector** and select your model provider
+3. Configure the connector with your API credentials and preferred model
+4. Search for **GenAI Settings** in the global search field
+5. Select your new connector from the **Default AI Connector** dropdown under **Custom connectors**
+6. Save your changes
+
+For detailed instructions on creating connectors, refer to [Connectors](https://www.elastic.co/docs/deploy-manage/manage-connectors).
+
+Learn more about [preconfigured connectors](https://www.elastic.co/docs/reference/kibana/connectors-kibana/pre-configured-connectors).
+
+#### Connect a local LLM
+
+You can connect a locally hosted LLM to Elastic using the OpenAI connector. This requires your local LLM to be compatible with the OpenAI API format.
+
+Refer to the [OpenAI connector documentation](kibana://reference/connectors-kibana/openai-action-type.md) for detailed setup instructions.
+
+## Connectors API
+
+For programmatic access to connector management, refer to the [Connectors API documentation]({{kib-serverless-apis}}group/endpoint-connectors).
+
+## Recommended models
+
+{{agent-builder}} requires models with strong reasoning and tool-calling capabilities. State-of-the-art models perform significantly better than smaller or older models.
+
+The following models are known to work well with {{agent-builder}}:
+
+- **OpenAI**: GPT-4.1, GPT-4o
+- **Anthropic**: Claude Sonnet 4.5, Claude Sonnet 4, Claude Sonnet 3.7
+- **Google**: Gemini 2.5 Pro
+
+### Why model quality matters
+
+Agent Builder relies on advanced LLM capabilities including:
+
+- **Function calling**: Models must accurately select appropriate tools and construct valid parameters from natural language requests
+- **Multi-step reasoning**: Agents need to plan, execute, and adapt based on tool results across multiple iterations
+- **Structured output**: Models must produce properly formatted responses that the agent framework can parse
+
+Smaller or less capable models may produce errors like:
+
+```console-response
+Error: Invalid function call syntax
+```
+
+```console-response
+Error executing agent: No tool calls found in the response.
+```
+
+While any chat-completion-compatible connector can technically be configured, we strongly recommend using state-of-the-art models for reliable agent performance.
+
+:::{note}
+GPT-4o-mini and similar smaller models are not recommended for {{agent-builder}} as they lack the necessary capabilities for reliable agent workflows.
+:::
+
+## Related resources
+
+- [Limitations and known issues](limitations-known-issues.md): Current limitations around model selection
+- [Get started](get-started.md): Initial setup and configuration
+- [Connectors](/deploy-manage/manage-connectors.md): Detailed connector configuration guide

solutions/search/elastic-agent-builder.md

@@ -54,6 +54,13 @@ To get started you need an Elastic deployment and you must enable the feature.
 
 [**Get started with {{agent-builder}}**](agent-builder/get-started.md)
 
+## Model selection
+
+By default, agents use the Elastic Managed LLM, but you can configure other model providers using connectors, including local LLMs deployed on your infrastructure.
+
+[**Learn more about model selection**](agent-builder/models.md)
+
+
 ## Programmatic interfaces
 
 {{agent-builder}} provides APIs and LLM integration options for programmatic access and automation.