Model request tags documentation (#20290)

* Add request tags documentation for spend tracking

- Add new concise doc explaining how to tag model requests
- Include Python SDK and cURL examples
- Show where tags appear in spend logs
- Add common use cases table (AWS accounts, teams, projects)
- Include how to set default tags on API keys
- Add to Spend Tracking section in sidebar

Co-authored-by: ishaan <ishaan@berri.ai>

* Simplify request tags doc for AI Gateway usage

- Focus on config.yaml setup with default_key_generate_params
- Show both request body and header methods for sending tags
- Remove SDK examples, keep concise cURL examples
- Streamline for quick reference

Co-authored-by: ishaan <ishaan@berri.ai>

* Update request tags doc to show model-level config

- Set tags directly on model deployments in litellm_params
- Requests just specify model, tags applied automatically
- Use clear naming: AWS_IAM_PROD, AWS_IAM_DEV

Co-authored-by: ishaan <ishaan@berri.ai>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: ishaan <ishaan@berri.ai>

docs/my-website/docs/proxy/request_tags.md

@@ -0,0 +1,58 @@
+# Request Tags for Spend Tracking
+
+Add tags to model deployments to track spend by environment, AWS account, or any custom label.
+
+Tags appear in the `request_tags` field of LiteLLM spend logs.
+
+## Config Setup
+
+Set tags on model deployments in `config.yaml`:
+
+```yaml title="config.yaml"
+model_list:
+  - model_name: gpt-4
+    litellm_params:
+      model: azure/gpt-4-prod
+      api_key: os.environ/AZURE_PROD_API_KEY
+      api_base: https://prod.openai.azure.com/
+      tags: ["AWS_IAM_PROD"]  # 👈 Tag for production
+
+  - model_name: gpt-4-dev
+    litellm_params:
+      model: azure/gpt-4-dev
+      api_key: os.environ/AZURE_DEV_API_KEY
+      api_base: https://dev.openai.azure.com/
+      tags: ["AWS_IAM_DEV"]  # 👈 Tag for development
+```
+
+## Make Request
+
+Requests just specify the model - tags are automatically applied:
+
+```bash
+curl -X POST 'http://0.0.0.0:4000/chat/completions' \
+  -H 'Authorization: Bearer sk-1234' \
+  -H 'Content-Type: application/json' \
+  -d '{
+    "model": "gpt-4",
+    "messages": [{"role": "user", "content": "Hello"}]
+  }'
+```
+
+## Spend Logs
+
+The tag from the model config appears in `LiteLLM_SpendLogs`:
+
+```json
+{
+  "request_id": "chatcmpl-abc123",
+  "request_tags": ["AWS_IAM_PROD"],
+  "spend": 0.002,
+  "model": "gpt-4"
+}
+```
+
+## Related
+
+- [Spend Tracking Overview](cost_tracking.md)
+- [Tag Budgets](tag_budgets.md) - Set budget limits per tag

docs/my-website/sidebars.js

@@ -442,6 +442,7 @@ const sidebars = {
           label: "Spend Tracking",
           items: [
             "proxy/cost_tracking",
+            "proxy/request_tags",
             "proxy/custom_pricing",
             "proxy/pricing_calculator",
             "proxy/provider_margins",