Fetching from the wire…
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Public story · 2026-08-03 · high
Confirming a tool call now resends the whole request, doubling payload for thousand-token tools, per paddo.dev.
Why now: The spec's stateless session revision landed July 28, and paddo.dev's breakdown of its confirmation-flow cost appears in coverage dated August 3.
MCP's July 28 stateless spec revision forces confirmations to resend the entire original request, per paddo.dev's writeup on the change.
For tools that pass thousand-token arguments, that doubles the payload sent on every confirm. Whether the duplicate also lands in the model's context window isn't settled by the spec. Paddo.dev says that depends on the client, so you have to check your own implementation rather than assume either way.
The same design has a real upside. Deterministic tool ordering plus freshness hints let a stateless server get cached in ways a session-bound one couldn't.
That's the trade: the spec gave up server-held state, and confirm-heavy tools now foot the bill in wire traffic. Teams that build the caching side of this will save on repeat calls. Teams that skip the audit will just pay more per round trip.
Paddo.dev's advice is blunt: audit your confirm-heavy tools before anything else in the migration.
Each link below shares sources, entities, or timing with this story.
Shared entity: Audit / Same source domain / Shared topic / Earlier coverage
Both cover Audit; reported by the same outlet (paddo.dev); overlapping topics (audit, context).
Shared entity: Audit / Shared topic / Earlier coverage / Tension
Both cover Audit; overlapping topics (audit, context); earlier Audit coverage from 2026-06-28.
Both cover Audit; overlapping topics (server, tool); earlier Audit coverage from 2026-03-23.
Both cover Audit; overlapping topics (context, server); earlier Audit coverage from 2026-03-22.
Both cover Audit; overlapping topics (audit, context); earlier Audit coverage from 2026-03-02.
Both cover Audit; overlapping topics (audit, server); earlier Audit coverage from 2026-02-26.
Both cover Audit; overlapping topics (audit, tool); earlier Audit coverage from 2026-02-21.
Shared entity: Audit / Shared topic / Earlier coverage
Both cover Audit; overlapping topics (audit, cost, tool); earlier Audit coverage from 2026-07-30.