What is truss-tool-error-states?

A set of instructions for how Truss runs tools and displays their progress, results, and errors. Tools are actions an AI agent can call, including built-in tools and MCP tools, which are tools provided through an external connection standard.

Use it when changing tool execution, tool-call streaming, MCP integrations, provider recovery, saved thinking data, or the chat interface for tool and sub-agent status updates.

It keeps failed tool calls visible and preserves the agent's reasoning and error details instead of replacing them with a vague failure message. It also ensures that progress and completion states are represented consistently.

How truss-harness/Truss configures Codex

Reuse

Borrowing it

Nothing to install: this file belongs to truss-harness/Truss. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/truss-harness/Truss/master/.skills/truss-tool-error-states/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/truss-harness/Truss

Made for: Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/truss-harness/truss/truss-tool-error-states/github.svg)](https://agentmods.dev/skills/truss-harness/truss/truss-tool-error-states)

Your own site

<a href="https://agentmods.dev/skills/truss-harness/truss/truss-tool-error-states"><img src="https://agentmods.dev/badge/skills/truss-harness/truss/truss-tool-error-states/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/truss-harness/truss/truss-tool-error-states"><img src="https://agentmods.dev/badge/skills/truss-harness/truss/truss-tool-error-states.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 150 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,621 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00150	$0.01621
Opus 5.5	$0.00060	$0.00648
Sonnet 5.5	$0.00030	$0.00324
Haiku 4.5	$0.00015	$0.00162

Measured 2mo ago against content hash 0741567308b7, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

truss-tool-error-states scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.skills/truss-tool-error-states/SKILL.md · 60 lines

How it starts

The opening of the file, as written. The whole thing — 60 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Truss Tool Error States

Use this skill before changing native tools, MCP tool execution, or tool-call presentation.

Error Contract

Preserve the assistant's thinking state when tools fail. Do not replace accumulated thinking or tool-call rows with a generic provider or stream error.
Every attempted tool call should emit a visible tool_call update with status: "running", then exactly one terminal update with status: "completed" or status: "error".
Long-running MCP tools may emit progress before the terminal update. Preserve progress as ChatToolCall.progress on repeated tool_call events for the same call ID; do not treat progress as a separate tool result.
When progress reaches 100, keep that progress value on the terminal update so the transcript can hold the completed bar briefly before fading it out.
spawn_sub_agent calls should also emit sub_agent.spawned and terminal sub_agent.status updates. Failed children must leave the parent tool call in status: "error" with the child session reference preserved.
Store failed tool calls in ChatThinking.toolCalls with the original arguments, title, timestamps, and full error string so the transcript detail modal can show what happened.
If all tool calls in a tool turn fail, return an assistant message that summarizes the concrete tool failures and includes the merged thinking/tool metadata. Do not continue into a provider call that only sees tool_error messages unless at least one tool call succeeded or there is a deliberate recovery path.
If a stream-level error still occurs after tool events have arrived, the client should preserve the in-flight assistant message and only mark it status: "error".
Provider text-call marker syntax such as Kimi, DSML, or MiniMax <tool_call><invoke name="...">... blocks should be recovered into internal tool calls and stripped from final assistant content, not written into the transcript as ordinary text.
Prefer specific user-visible messages such as Web search: query failed because ... over vague text like Error in input stream.

Read the full file on GitHub · 60 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

agents/openai.yaml 233 B

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 60 lines · 150 tokens per session scan A 0741567308b7

Subscribe to this mod's changes

truss-tool-error-states is a skill published in the GitHub repository truss-harness/Truss (5 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 150 tokens to every session and 1,621 once invoked, about $0.0006 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Building agents Debugging LLM ai ai-agents harness

truss-tool-error-states next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
truss-tool-error-statestruss-harness/Truss	Skill	5	3mo ago	Apache-2.0	A	150	Codex
debugStepfenShawn/kota	Skill	101	2d ago	MIT	A	6	Claude Code, Codex
systematic-debuggingNousResearch/hermes-agent	Skill	261k	yesterday	MIT	A	16	Claude Code, Codex
python-debugpyNousResearch/hermes-agent	Skill	261k	yesterday	MIT	B	17	Claude Code, Codex
sglang-diffusion-benchmark-profilesgl-project/sglang	Skill	39k	yesterday	Apache-2.0	A	26	Claude Code, Codex
resolve-handoffomnigent-ai/omnigent	Skill	11k	yesterday	Apache-2.0	A	23	Claude Code, Codex
iterate-implementationhumanlayer/humanlayer	Skill	13k	yesterday	Apache-2.0	A	16	Claude Code, Codex

Truss: Skill for Codex