Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/liuyihey/agent-engineering/tool-call-fixnpx skills add LiuYihey/Agent-Engineering --skill tool-call-fixgit clone --depth 1 https://github.com/LiuYihey/Agent-EngineeringWrote 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.
[](https://agentmods.dev/skills/liuyihey/agent-engineering/tool-call-fix)<a href="https://agentmods.dev/skills/liuyihey/agent-engineering/tool-call-fix"><img src="https://agentmods.dev/badge/skills/liuyihey/agent-engineering/tool-call-fix.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00081 | $0.01979 |
| Opus 5 | $0.00041 | $0.00989 |
| Sonnet 5 | $0.00016 | $0.00396 |
| Haiku 4.5 | $0.00008 | $0.00198 |
Grade A, and why
tool-call-fix 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 5d 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.
How it starts
The opening of the file, as written. The whole thing — 162 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Tool Call Fix
Systematic playbook for "the agent said it would call a tool, but nothing happened" and related failures.
Works on any stack (raw SDK, LangChain, LangGraph, Vercel AI SDK, custom agent loops). Project-specific notes live in examples/ — add your own file there when adapting.
Core mental model
Prose and tool execution are two weakly coupled channels:
LLM stream
├─ text_delta → UI text (usually immediate)
├─ thinking_delta → "Thought for Ns" / hidden reasoning (immediate)
└─ tool_use block → parser → executor → tool card (often delayed)
Never infer tool execution from assistant prose. Only structured tool_use / function_call blocks count.
UI transcript ≠ LLM transcript. Chat history shown to users is often flattened text. The API needs structured blocks (thinking, tool_use, tool_result). Rebuilding API input from UI text alone causes Mode H — tools look "broken" on turn 2+ even when turn 1 worked.
Before you patch: classify the layer
Same user symptom can break at eight layers (A–H). Classify with logs before adding nudges, tool_choice: required, or prompt changes.
| Log / signal | Mode | Fix layer |
|---|---|---|
Raw stream has no tool block; stop_reason=end_turn |
A Wire prose-only | Model/guard; not parser |
| Turn 1 OK, turn 2+ degrades; flat API history | H Transcript loss | Persist native message chain |
tool_calls=1 but wrong name vs intent |
B Wrong tool | Routing/prompt; recovery won't fire |
| Right tool, executor rejects input | C Bad payload | Schema validation / coercion |
| Parser has tool block; UI late or silent mid-stream | D Stream bridge | Forward early tool events to UI |
| Second round in same turn breaks | E In-turn thinking loss | Preserve thinking + signature in working messages |
| Server logs exec; UI/DB silent | F Visibility filter | Align skip/hide lists across layers |
| Guard should fire; didn't | G Dead guard branch | Fix intent detection patterns |
What ships with it
3 files 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.
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.
- 5d ago First seen · 162 lines · 81 tokens per session scan A 4d7a2869622e
tool-call-fix is a skill published in the GitHub repository LiuYihey/Agent-Engineering (5 stars, last pushed 1mo ago), licensed MIT. It adds 81 tokens to every session and 1,979 once invoked, about $0.0004 per session on Opus 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.
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