FreshCtx: pre-action freshness protection for MCP tools at tools/call

[bhooshanvarma]

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I built a pre-action freshness guard for consequential MCP tool calls.

The failure case is narrow: an agent can make a valid decision from current evidence, but that evidence can change before the MCP tool executes.

FreshCtx 0.9.0 adds protection at the native tools/call boundary. Immediately before a configured tool handler runs, FreshCtx revalidates the evidence declared for that action.

A reproducible scenario:

1. Agent observes available_balance = $10,000
2. Agent decides an $8,000 transfer is valid
3. Balance changes to $2,000
4. The MCP tool call begins
5. FreshCtx revalidates the declared balance dependency
6. Result: STALE_REASONING
7. The protected handler does not execute

The outcomes are explicit:

• CURRENT → protected handler proceeds
• STALE_REASONING → blocked before the handler
• UNVERIFIABLE → blocked because required evidence could not be confirmed

Multiple protected tools can have independent dependency sets, so stale evidence affecting one tool does not automatically block unrelated tools.

The main design challenge was keeping this boundary narrow. FreshCtx does not replace MCP authentication, authorization, transaction controls, idempotency, or tool-level safety.

It asks one additional question immediately before the protected action:

Is the evidence that justified this specific tool call still current?

I would especially value feedback from MCP server authors on whether tools/call is the right boundary for this check in real MCP architectures.

Relevant Links

GitHub:
https://github.com/Hyperwise-LLC/freshctx

MCP Guard documentation:
https://github.com/Hyperwise-LLC/freshctx/blob/main/docs/MCP_GUARD.md

Runnable three-outcome demo:
https://github.com/Hyperwise-LLC/freshctx/blob/main/examples/mcp_balance_guard.py

PyPI:
https://pypi.org/project/freshctx/0.9.0/

freshctx-mcp-stale-action-demo.mp4