Install setup (#98)

Author: samuelcolvin

docs/api/models/function.md

@@ -1,3 +1,10 @@
 # `pydantic_ai.models.function`
 
+A model controlled by a local function.
+
+[`FunctionModel`][pydantic_ai.models.function.FunctionModel] is similar to [`TestModel`][pydantic_ai.models.test.TestModel],
+but allows greater control over the model's behavior.
+
+Its primary use case is for more advanced unit testing than is possible with `TestModel`.
+
 ::: pydantic_ai.models.function

docs/api/models/gemini.md

@@ -1,3 +1,20 @@
 # `pydantic_ai.models.gemini`
 
+Custom interface to the `generativelanguage.googleapis.com` API using
+[HTTPX](https://www.python-httpx.org/) and [Pydantic](https://docs.pydantic.dev/latest/.
+
+The Google SDK for interacting with the `generativelanguage.googleapis.com` API
+[`google-generativeai`](https://ai.google.dev/gemini-api/docs/quickstart?lang=python) reads like it was written by a
+Java developer who thought they knew everything about OOP, spent 30 minutes trying to learn Python,
+gave up and decided to build the library to prove how horrible Python is. It also doesn't use httpx for HTTP requests,
+and tries to implement tool calling itself, but doesn't use Pydantic or equivalent for validation.
+
+We therefore implement support for the API directly.
+
+Despite these shortcomings, the Gemini model is actually quite powerful and very fast.
+
+## Setup
+
+For details on how to set up authentication with this model, see [model configuration for Gemini](../../install.md#gemini).
+
 ::: pydantic_ai.models.gemini

docs/api/models/groq.md

@@ -1,3 +1,7 @@
 # `pydantic_ai.models.groq`
 
+## Setup
+
+For details on how to set up authentication with this model, see [model configuration for Groq](../../install.md#groq).
+
 ::: pydantic_ai.models.groq

docs/api/models/openai.md

@@ -1,3 +1,7 @@
 # `pydantic_ai.models.openai`
 
+## Setup
+
+For details on how to set up authentication with this model, see [model configuration for OpenAI](../../install.md#openai).
+
 ::: pydantic_ai.models.openai

docs/api/models/vertexai.md

@@ -1,3 +1,52 @@
 # `pydantic_ai.models.vertexai`
 
+Custom interface to the `*-aiplatform.googleapis.com` API for Gemini models.
+
+This model uses [`GeminiAgentModel`][pydantic_ai.models.gemini.GeminiAgentModel] with just the URL and auth method
+changed from [`GeminiModel`][pydantic_ai.models.gemini.GeminiModel], it relies on the VertexAI
+[`generateContent`](https://cloud.google.com/vertex-ai/docs/reference/rest/v1/projects.locations.endpoints/generateContent)
+and
+[`streamGenerateContent`](https://cloud.google.com/vertex-ai/docs/reference/rest/v1/projects.locations.endpoints/streamGenerateContent)
+function endpoints
+having the same schemas as the equivalent [Gemini endpoints][pydantic_ai.models.gemini.GeminiModel].
+
+There are four advantages of using this API over the `generativelanguage.googleapis.com` API which
+[`GeminiModel`][pydantic_ai.models.gemini.GeminiModel] uses, and one big disadvantage.
+
+## Setup
+
+For details on how to set up authentication with this model as well as a comparison with the `generativelanguage.googleapis.com` API used by [`GeminiModel`][pydantic_ai.models.gemini.GeminiModel],
+see [model configuration for Gemini via VertexAI](../../install.md#gemini-via-vertexai).
+
+## Example Usage
+
+With the default google project already configured in your environment using "application default credentials":
+
+```py title="vertex_example_env.py"
+from pydantic_ai import Agent
+from pydantic_ai.models.vertexai import VertexAIModel
+
+model = VertexAIModel('gemini-1.5-flash')
+agent = Agent(model)
+result = agent.run_sync('Tell me a joke.')
+print(result.data)
+#> Did you hear about the toothpaste scandal? They called it Colgate.
+```
+
+Or using a service account JSON file:
+
+```py title="vertex_example_service_account.py"
+from pydantic_ai import Agent
+from pydantic_ai.models.vertexai import VertexAIModel
+
+model = VertexAIModel(
+    'gemini-1.5-flash',
+    service_account_file='path/to/service-account.json',
+)
+agent = Agent(model)
+result = agent.run_sync('Tell me a joke.')
+print(result.data)
+#> Did you hear about the toothpaste scandal? They called it Colgate.
+```
+
 ::: pydantic_ai.models.vertexai

docs/examples/index.md

@@ -20,12 +20,9 @@ If you clone the repo, you should instead use `uv sync --extra examples` to inst
 
 ### Setting model environment variables
 
-All these examples will need you to set either:
+These examples will need you to set up authentication with one or more of the LLMs, see the [model configuration](../install.md#model-configuration) docs for details on how to do this.
 
-* `OPENAI_API_KEY` to use OpenAI models, go to [platform.openai.com](https://platform.openai.com/) and follow your nose until you find how to generate an API key
-* or, `GEMINI_API_KEY` to use Google Gemini models, go to [aistudio.google.com](https://aistudio.google.com/) and do the same to generate an API key
-
-Then set the API key as an environment variable with:
+TL;DR: in most cases you'll need to set one of the following environment variables:
 
 === "OpenAI"