problem-decoder

problem-decoder is a skill for Claude Code, Codex from Far-200/think-before-code. It costs 70 tokens per session (1,542 once invoked), scanned A, original, MIT.

A guided reading workflow for DSA, or data-structures-and-algorithms, and LeetCode-style problem statements. It helps a learner identify the inputs, outputs, limits, and edge cases before solving.

In plain words
What is it for?
Use it to clarify a programming problem before moving on to a separate skill for choosing an algorithm or data structure.
Why use it?
It reduces mistakes caused by solving a slightly different problem than the one that was asked. It deliberately does not design the solution approach.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to clarify a programming problem before moving on to a separate skill for choosing an algorithm or data structure.

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Install with agentmods
npx agentmods add skills/far-200/think-before-code/problem-decoder
Install

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.

Any agent
npx skills add Far-200/think-before-code --skill problem-decoder
Clone the repo
git clone --depth 1 https://github.com/Far-200/think-before-code

Made for: Claude Code, 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.

agentmods badge for problem-decoder

README.md
[![agentmods](https://agentmods.dev/badge/skills/far-200/think-before-code/problem-decoder/github.svg)](https://agentmods.dev/skills/far-200/think-before-code/problem-decoder)
Your own site
<a href="https://agentmods.dev/skills/far-200/think-before-code/problem-decoder"><img src="https://agentmods.dev/badge/skills/far-200/think-before-code/problem-decoder/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.

agentmods 80×15 button for problem-decoder

Your own site · 80×15
<a href="https://agentmods.dev/skills/far-200/think-before-code/problem-decoder"><img src="https://agentmods.dev/badge/skills/far-200/think-before-code/problem-decoder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 70 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,542 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00070 $0.01542
Opus 5.5 $0.00028 $0.00617
Sonnet 5.5 $0.00014 $0.00308
Haiku 4.5 $0.00007 $0.00154

Measured 1mo ago against content hash 5abab363804e, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

problem-decoder 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 1mo 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/problem-decoder/SKILL.md · 173 lines

How it starts

The opening of the file, as written. The whole thing — 173 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Problem Decoder

Why this exists

A large share of DSA mistakes are not reasoning errors at all — they are reading-error: the learner solved a problem slightly different from the one that was actually asked. dsa-tutor assumes the problem has already been read correctly and starts from "describe a brute-force approach." This skill is the step before that: force a precise reading before any solving instinct kicks in.

This skill never designs an approach, names a pattern, or gives a hint toward a solution. Once the problem is fully decoded, hand the learner back to dsa-tutor.

Circuit breaker

Before letting the conversation move toward "how would you solve this," check silently:

Has the learner stated, in their own words, the input format,
output format, constraints, and at least one non-obvious edge case?

  NO  → stay here. Ask about the missing piece specifically.
  YES → decoding is done. Point them to dsa-tutor for the approach.

Hard stop: if you're about to say "so the approach here would be" or name a pattern — stop. That is not this skill's job.

What to extract

Work through these one at a time, not as a dumped checklist. Ask the learner to state each one first; only add what they missed.

  1. Input — exact types, shape, and any stated bounds (array length, value range, whether it's sorted, whether values repeat).
  2. Output — exact format expected, and what "correct" means when multiple valid answers could exist (any valid one? the smallest? in original order?).
  3. Constraints — the numeric bounds (e.g. n ≤ 10^5). Ask the learner what those bounds imply about the complexity the problem is expecting — this is a mechanical reading skill most learners skip, and it belongs here, not in complexity-coach (which analyzes an approach the learner already has, not the problem's expected ceiling).
  4. Edge cases — both the ones the statement mentions explicitly and the ones it implies (empty input, single element, all duplicates, negative numbers, integer overflow). This is reading the statement's edges before any solving — constructing a systematic, executable test suite for an approach the learner already has belongs to test-case-coach, not here.
  5. Ambiguities — anything the statement leaves unresolved that the learner needs to decide on (tie-breaking rules, mutability of input, whether order matters).

Read the full file on GitHub · 173 lines

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.

  1. 1mo ago First seen · 173 lines · 70 tokens per session scan A 5abab363804e

Subscribe to this mod's changes

problem-decoder is a skill published in the GitHub repository Far-200/think-before-code (16 stars, last pushed 1mo ago), licensed MIT. It adds 70 tokens to every session and 1,542 once invoked, about $0.0003 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.

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