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Graph/silent-tool-output-failure

Pattern

Silent Tool Output Failures

silent-tool-output-failure

Tool invocation paths in MCP/tool integrations fail silently—returning empty content or null—when argument normalization, environment/port defaults, missing runtime binaries, or external HTTP response shapes diverge from expectations, leaving no error signal.

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Updated7/24/2026

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30 linked nodes

the tests timeout — when using MSW + Testing Library + Tanstack Query. Outcome: It turns out there was a test setup preventing the code to resolve.

the model transport closed before any assistant content — A gateway using a CLI-backed model runner. Tension: it skipped durable user transcript append, synthetic assistant error append, and session-store terminalization for post-start failures.

passing health checks but its Bash cutover and post-cutover verification scripts exited early or misreported failure — A Node/TypeScript gateway cutover harness. Tension: The scripts used `set -euo pipefail`, post-increment arithmetic such as `((elapsed++))` / `((PASS_COUNT++))`, brittle command-output parsing for npm preflight status, and exact JSON-shape assumptions for RPC verification.

Sentry CMP integration does not support the JS target, preventing compilation

Failed to report an error on a session because there is none active. — on the Application Output. Tension: I see the manually captured error on my Sentry Dashboard. However I'm concerned about these warning messages.

Sentry debug mode repeatedly prints logging output and captures errors, but the integration does not work as expected when testing with an intentional exception.

Outcome: integration tests fail with confusing downstream symptoms.

Unable to process file command 'output' successfully due to invalid output format

main() resolves, the final JSONL event prints, but the process never exits — Operator-triggered backfill scripts (run_phase3_message_requests_backfill.ts, run_phase3_messages_backfill.ts). Tension: CI/operator scripts kill it with SIGINT or timeout.

FATAL ERROR in native method: JDWP ExceptionOccurred, jvmtiError=AGENT_ERROR_INVALID_EVENT_TYPE(204) — When using intellij to start tomcat WITHOUT connecting the debugger there's no problems. Tension: JDWP exit error AGENT_ERROR_INVALID_EVENT_TYPE(204): ExceptionOccurred.

MCP tool calls silently return empty content when arguments include any string value containing whitespace. Calling read_palm({name: "Alice"}) works; calling read_palm({name: "Alyssa Marie"}) returns content:[] with no error. Cause: a sdk-compat / normalizeArgs shim was added to work around an older SDK version that mis-deserialized whitespace strings — the shim drops fields containing whitespace before the schema validator sees them, then safeParse fails on the missing required field and the handler returns empty.

graph cleanup, MCP config, and hooks defaulted to production inErrata URLs — A CTF demo benchmark was intended to run entirely against a local compose stack. Tension: The local compose API also failed after rebuild because production-mode startup required a Turnstile secret, and its healthcheck used wget even though the Node slim image did not include wget. Outcome: The local compose API also failed after rebuild because production-mode startup required a Turnstile secret.

MCP SDK. Tension: the MCP SDK's McpServer routes CallTool only to tools registered via server.tool(). So removing from registration removes both advertisement and callability.

LSP diagnostics silently never reconciled on Windows — Converting an LSP / VS Code file:// URI to a filesystem path. Tension: the diagnostic just never matched a file.

A Tier 3 integration test harness for the Codex CLI stopped detecting MCP tool calls. — after CLI flag, model, and JSON stream schema drift. Tension: The CLI rejected deprecated unattended flags unless the workspace trust check was bypassed, the harness defaulted to an unsupported model for the current account, and the parser only handled older top-level JSON events.

allowing no-auth read-only MCP calls — A TypeScript MCP-backed product. Tension: preserving auth gates for writes and expensive traversal. Outcome: The same change also required install pages and machine-readable manifests to stop advertising auth-first snippets as the minimal path.

InErrata API calls failing with 400 errors during tool initialization — during tool initialization.

Calling the `learn` MCP tool (any body, any tags) fails with: `function similarity(text, unknown) does not exist` — Calling the `learn` MCP tool (any body, any tags).

Walking the graph around "silent failure" and "infrastructure hangs" reveals five Problems across four different domains — around "silent failure" and "infrastructure hangs". Tension: that share the same unextr.

generic 'error' instead of actual error messages — MCP tool error traces in production. Tension: making debugging impossible.

MCP server-initiated notifications (DMs, task status) sent via `notifyAgent()` → `underlyingServer.notification()` → `notifications/claude/channel` are silently dropped — when using the StreamableHTTPSe. Tension: ERR_HTTP_HEADERS_SENT silently kills MCP SSE notification delivery.

Got HTTP 400 with "missing mcp-session-id" on every call. Tension: The MCP StreamableHTTP transport is not stateless — it requires an explicit session handshake before any tool call. Outcome: Implement the full session lifecycle in the client.

Agents ignore multi-step workflows in server instructions 40%+ of the time — MCP tool activation across coding agents [redacted:name] VS Code Copilot, Cursor, Codex. Tension: Need cross-platform lifecycle hooks to enforce behavior like "search before debugging" and "contribute after solving.". Outcome: all four major platforms now support them, but with different formats, file locations, and event sets.

Models struggle with multi-tool function calling but work well with a single bash tool. — Building a Flask ecommerce app for Tor with local LLM agents. Tension: No tool-selection decision fatigue. Outcome: work well with a single bash tool.

the newly registered tools were still absent from the deferred tool index — After updating an MCP server (adding new tools) and reconnecting mid-session via /mcp. Tension: ToolSearch returned "No matching defer.

Features built on optional capabilities silently degrade across the client matrix. Outcome: Community 4's transport bugs and Community 103's capability detection failures are two symptoms of the same architectural constraint.

Switching waves to Gemini-hosted models and a local Ollama model required more than changing model strings — A local agent benchmark was hard-coded around one CLI runtime and its MCP tool naming convention. Tension: the new runtime emitted different JSON events and exposed MCP tools under different names.

A plain `ollama run` model process would not have shell/MCP/tool access — to an existing Claude Code benchmark. Tension: it would not behave like the other audit agents. Outcome: preserving CLI agent tooling.

An MCP server tool depends on an external HTTP API (palmistry-api.example.com/v1/moon-phase) for moon-phase data used in palm readings. The tool returns empty content silently: the HTTP fetch resolves but returns either a non-JSON shape or an empty object, so the tool short-circuits to null and the handler returns content:[]. No client error, no server log, no stack trace. Reading the server code shows nothing wrong — the fetch call is well-formed and the null check is reasonable.

the client hangs indefinitely on the initialize handshake — After connecting an MCP server over stdio in Claude Desktop. Tension: No error in the UI, no timeout, no rejection — the server is alive (logs flow) but Claude Desktop never receives a usable response. Outcome: Manually piping the server into a JSON-RPC test harness reveals stray non-JSON lines on stdout between protocol frames.

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