Tool-result size governor for MCP — by TextForAgents LLC. MCP defines no limit on tool-result size, so one unbounded result from a third-party server you don't control can blow your agent's entire context window — or deadlock its stdio transport. Runpod's own audit found a single unpaginated list call at ~15× Claude Code's context window; a production post-mortem traced a ~2.1 MB result to a stdio SIGPIPE deadlock whose fix eliminated 12 incidents in 6 weeks. Every published fix is server-side — useless across the 40,047 third-party servers you cannot patch. This governor is a client-side proxy you point your agent at once, in front of any MCP server: per-route ceilings in tokens/records/bytes, structure-aware windowing (array slices with total/returned/omitted counts, log head+tail, prose sectioning), the full payload spilled to a checksummed expiring artifact with a fetch-narrower-slice route, an HMAC-signed omission receipt on every shaped result proving what was held back — never silent truncation — a repeat-everything denial that lives exactly as long as its spill, and backpressure-safe forwarding so a 2 MB result cannot SIGPIPE the session. Proven in the lab: 51/51 tests including the 2.1 MB deadlock fixture (client bytes bounded at 24,469, no deadlock), shaping ~$1–2×10⁻⁸/result. Operator $9/mo · Fleet $29/mo · Per-result API $0.001/result. First 100 shaped results free, one time per operator.
Operator $9/mo per operator · Fleet $29/mo per operator · Per-result API $0.001/result (x402). First 100 shaped results free, one time per operator. There is no perpetual free tier.
Honest bounds: HTTP transport is built in this hosted surface and the client-side stdio proxy package; shaping correctness was measured structurally (exact counts, byte-exact re-fetch), not by a live-model task-completion study — no task-completion equivalence is claimed. Receipt expires_at is an upper bound: quota eviction under the bounded spill store can retire an artifact earlier, in which case a slice fetch returns a clean unknown_artifact error and the identical query re-opens exactly once. The downloadable client-side proxy package is distribution, not metered free use; the one-time trial binds hosted use.
How it works: POST /register for a token, POST /shape with a tool result (raw text, an MCP result envelope, or a built-in fixture tool) under a route name, read the shaped window + signed omission receipt, POST /fetch-slice to re-fetch a narrower slice byte-exact, POST /budgets to set per-route ceilings. Or run the stdio proxy package in front of your own MCP server.
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