Bug Report: An assistant using the Strava MCP connector underestimated a user's training history

Components: Strava MCP connector (list_activities), Claude (claude-sonnet-5)

Athlete: Daniel Griffin on Strava · UltraSignup results

Date observed: 2026-09-18

Severity: Moderate. The user got a wrong assessment of their fitness history, stated with confidence.

Status: Reported for discussion. This report doesn't claim a root cause.

User intent

The user asked for a marathon training plan based on their actual training history. They are a former ultramarathon runner returning to training, and wanted a plan that accounted for their long-term base rather than only their recent weeks.

What happened

The assistant retrieved activities since 2026-06-01. It found a longest recent run of about 5 miles and advised against a 10-week marathon build.
The user asked: "But you see my historical base?"
The assistant retrieved the 100 most recent activities, back to 2023-06-16. The response included has_next_page: true. The assistant reported: "Longest run ever logged: ~9.5 miles" and "he's never built marathon-distance mileage."
The user pasted race results from UltraSignup, including a 200-mile finish in 2017.
The assistant said those races predated the Strava account.
A later date-filtered query (2015–2018) returned the 2017 data from the same account, including an activity titled "Recovery Run from Bigfoot 200."

Expected behavior

The assistant should understand the scope of the training data it has retrieved and keep its claims within that scope. If the available data cannot support a conclusion about the user's full history, it should make that uncertainty explicit.

Friction observed

In the connector

The tool description says nothing about how much of the history one call returns, or how to reach the rest.
A call with no arguments returns the 30 most recent activities.
Responses don't include a total activity count or the date of the oldest activity. The only sign that more data exists is has_next_page.
There's no single tool for retrieving the full history.
Strava's launch announcement promises access to users' "full training history." The help documentation says nothing about date ranges or pagination.

In the conversation

The assistant didn't tell the user which date range each query covered.
It stated conclusions about the user's whole history ("ever," "never") after retrieving only part of it.
It gave a reason for the missing data (that the account didn't exist yet) without checking it.
The pasted race results ran two fields together, so division place and finish time appeared as one string. The assistant read them without separating them and reported a 200-mile time of 46:20. The actual time was 96:20:18.

Notes

The connector's date filters and pagination worked correctly when used.
Searching for similar public reports found none. The connector began rolling out the week of June 1, 2026.