Updating uptime-monitoring docs to include uptime request spans (#14765)

## DESCRIBE YOUR PR
We are introducing uptime request spans to the uptime UX. These are out
of the box spans that come at no additional charge to the customer. We
need to update a few pages in order to reflect these changes:

- Main uptime monitoring documentation
(docs/product/uptime-monitoring/index.mdx)
- Uptime tracing documentation
(docs/product/uptime-monitoring/uptime-tracing.mdx)
- Product overview (docs/product/index.mdx)

Uptime monitoring doc:
https://sentry-docs-git-uptime-request-spans-updates.sentry.dev/product/uptime-monitoring/
Uptime tracing doc:
https://sentry-docs-git-uptime-request-spans-updates.sentry.dev/product/uptime-monitoring/uptime-tracing/
Product overview:
https://sentry-docs-git-uptime-request-spans-updates.sentry.dev/product/

## IS YOUR CHANGE URGENT?  

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to go live.
- [ ] Urgent deadline (GA date, etc.): <!-- ENTER DATE HERE -->
- [x] Other deadline: Some time week ending Sept 5th
- [ ] None: Not urgent, can wait up to 1 week+

## SLA

- Teamwork makes the dream work, so please add a reviewer to your PRs.
- Please give the docs team up to 1 week to review your PR unless you've
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Thanks in advance for your help!

## PRE-MERGE CHECKLIST

*Make sure you've checked the following before merging your changes:*

- [ ] Checked Vercel preview for correctness, including links
- [ ] PR was reviewed and approved by any necessary SMEs (subject matter
experts)
- [ ] PR was reviewed and approved by a member of the [Sentry docs
team](https://github.com/orgs/getsentry/teams/docs)

---------

Co-authored-by: Shannon Anahata <[email protected]>

Author: sfanahata

docs/product/index.mdx

@@ -50,7 +50,7 @@ Our [**AI Agents Monitoring**](/product/insights/ai/agents/) feature gives you i
 
 ### Uptime Monitoring
 
-Sentry's [**Uptime Monitoring**](/product/uptime-monitoring/) helps you maintain uptime for your web services by monitoring relevant URLs. It continuously tracks configured URLs, delivering alerts and insights to quickly identify downtime and troubleshoot issues. By leveraging [distributed tracing](/product/uptime-monitoring/uptime-tracing/), Sentry enables you to pinpoint any errors that occur during an uptime check, simplifying triage and accelerating root cause analysis.
+Sentry's [**Uptime Monitoring**](/product/uptime-monitoring/) helps you maintain uptime for your web services by monitoring relevant URLs. It continuously tracks configured URLs, delivering alerts and insights to quickly identify downtime and troubleshoot issues. By leveraging [distributed tracing](/product/uptime-monitoring/uptime-tracing/), Sentry enables you to pinpoint any errors that occur during an uptime check, simplifying triage and accelerating root cause analysis. Uptime monitoring includes [uptime request spans](/product/uptime-monitoring/#uptime-request-spans) by default. These act as the root of any uptime issue's trace, giving you better context for faster debugging. 
 
 ### Recurring Job Monitoring
 

docs/product/uptime-monitoring/img/allow-sampling-new.png

@@ -37,6 +37,22 @@ To prevent false alerts caused by temporary network issues, **an issue is only g
 
 _In rare cases where Sentry is unable to perform a scheduled uptime check—such as during outages—the check status will be marked as "Unknown"._
 
+## Uptime Request Spans
+
+Uptime checks include spans called _uptime request spans_ that Sentry automatically creates for the request. The `uptime.request` span acts as a root span for traces related to uptime checks. 
+
+![Uptime request span](./img/uptime-request-span.png)
+
+**Key Benefits:**
+
+- Context: You instantly know a trace was generated by an uptime check vs user traffic
+- Request lifecycle: You can see the full journey from the initial uptime check through your application's response
+- Enhanced debugging: You can see more details about exactly where and why the failure occurred to distinguish between uptime-related issues and other application problems
+
+<Alert type="info">
+Uptime request spans are free and will not count against your [span quota](/pricing/quotas/manage-transaction-quota/). These spans are always created, even if you have sampling disabled. 
+</Alert>
+
 ## Notifications
 
 To start getting notifications for a new downtime issue, [configure an issue alert](/product/alerts/create-alerts/issue-alert-config/) and choose the issue category "outage". Then choose how you'd like to be notified (via email, Slack, and so on).

docs/product/uptime-monitoring/img/uptime-allow-sampling.png

@@ -4,9 +4,15 @@ sidebar_order: 52
 description: "Learn how to use distributed tracing to troubleshoot downtime."
 ---
 
-Sentry's Uptime Monitoring uses [distributed tracing](/product/tracing/#whats-distributed-tracing) to track the flow and timing of requests and operations during uptime checks. This helps you quickly find the root cause of downtime by connecting related errors and performance data.
+Sentry's Uptime Monitoring uses [distributed tracing](/product/tracing/#whats-distributed-tracing) to track the flow and timing of requests and operations during uptime checks. This helps you quickly find the root cause of downtime by connecting related errors and performance data. 
 
-You can trace errors to identify and diagnose issues like crashes or exceptions. This is automatically enabled for all Uptime Alerts. You can also trace spans to monitor the performance and flow of operations, such as API calls or database queries. Span tracing is disabled by default, but can be enabled by allowing sampling in your Uptime Alert settings. Errors focus on problems, while spans focus on performance.
+When uptime checks are performed, Sentry creates a **trace** that shows the complete request lifecycle. This trace contains:
+
+- **Uptime request spans**: A [default set of root spans](/product/uptime-monitoring/#uptime-request-spans) that identifies this as an uptime check
+- **Application spans**: Individual operations like database queries, API calls, and cache operations, configured through distributed tracing
+- **Error events**: Any exceptions or failures that occur during the request
+
+**Error tracing** captures when things go wrong, while **span tracing** shows the performance and flow of operations. Together, they provide complete visibility into why an uptime check failed. Span tracing is disabled by default for uptime checks, but can be enabled by allowing sampling in your [Uptime Alert settings](/product/alerts/create-alerts/uptime-alert-config/). Errors plus spans focus on problems, while uptime monitoring plus spans focus on performance.
 
 ## How Uptime Tracing Works
 
@@ -56,15 +62,23 @@ Sentry.init({
 
 ## Tracing Spans
 
-Unlike error tracing, span tracing is **disabled** by default for uptime checks, but can be enabled by allowing sampling in your Uptime Alert settings. Enabling span tracing can be helpful because it provides a detailed view of the timing and flow of requests and operations during uptime checks, which is especially useful for diagnosing timeouts or performance issues.
+There are two sets of spans avaialble for uptime checks: 
+1. **Uptime request spans**. These are automatically created by Sentry for every uptime check request. You can find them as the root of any uptime issue's trace.
+2. **Application spans**. These are spans that are configured through distributed tracing. You can find them as the children of uptime request spans.
+ 
+Unlike error tracing, span tracing that you configure is **disabled** by default for uptime checks, but can be enabled by allowing sampling in your [Uptime Alert settings](/product/alerts/create-alerts/uptime-alert-config/). Enabling span tracing can be helpful because it provides a detailed view of the timing and flow of requests and operations during uptime checks, which is especially useful for diagnosing timeouts or performance issues.
 
 ### Enabling Uptime Tracing for Spans
 
 To enable span tracing, modify your Uptime Alert settings with the "Allow Sampling" option. This will ensure that Sentry defers the sampling decision to your SDK, which will follow the trace sample rate you've configured.
 
 Because uptime requests won't override your SDK’s error sampling rate, some errors may not appear in traces if that rate is set to below 1.
 
-![Uptime Alert Allow Sampling Configuration](./img/uptime-allow-sampling.png)
+![Uptime Alert Allow Sampling Configuration](./img/allow-sampling-new.png)
+
+<Alert>
+  Uptime request spans will always be on, even if sampling is disabled. Uptime request spans are free and will not count against your [span quota](/pricing/quotas/manage-transaction-quota/). 
+</Alert>
 
 ### Custom Sampling