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 skills add leifericf/agentic-sdk --skill develop-at-replgit clone --depth 1 https://github.com/leifericf/agentic-sdkWrote 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/leifericf/agentic-sdk/develop-at-repl)<a href="https://agentmods.dev/skills/leifericf/agentic-sdk/develop-at-repl"><img src="https://agentmods.dev/badge/skills/leifericf/agentic-sdk/develop-at-repl/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.
<a href="https://agentmods.dev/skills/leifericf/agentic-sdk/develop-at-repl"><img src="https://agentmods.dev/badge/skills/leifericf/agentic-sdk/develop-at-repl.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00033 | $0.01476 |
| Opus 5.5 | $0.00013 | $0.00590 |
| Sonnet 5.5 | $0.00007 | $0.00295 |
| Haiku 4.5 | $0.00003 | $0.00148 |
Grade A, and why
develop-at-repl 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.
How it starts
The opening of the file, as written. The whole thing — 136 lines — stays where its author put it; the contents beside it link to each section on GitHub.
develop-at-repl
The interactive eval loop is the primary development rhythm, not a debugging aside. Write a form, evaluate it, read the returned value, adjust: data in, data out, no setup ceremony. Batch test runs are the exception, reached for at landing boundaries (see "When to leave the loop"), not the rhythm.
The host depends on the language: nREPL for Clojure, IEx for Elixir.
C and Zig have no eval loop; their fast inner cycle is a small
throwaway harness built and run in seconds (see run-spike). The code
standard is the relevant write-<lang> recipe; the boundary contract
is references/architecture.md; the module layout and dev loop live
in the descriptor's module map.
Connect once
Start the host (nREPL, IEx) and attach the editor's client. One
long-lived session; do not restart it per change. The running image is
the unit of work. Require the namespace you are shaping; reload it
(:reload, IEx recompile, or a fresh harness run) after edits to a
dependency.
If the project has no live host yet (a C or Zig unit, or a Clojure or Elixir project before the dev alias is wired), say so and fall back to reasoning over the source plus a fast harness. Do not fabricate a running image.
Procedure
- Evaluate one small form. Send the smallest form that answers the next question: a constructor call, a query against a literal input, a pure transform over a hand-built value. Read the returned value.
- Inspect the data, do not re-run a suite. The pure core takes
data and returns data; the answer is the value at the prompt. Drill
with the host's tools (pretty-print on a deep structure, an
inspector tap,
keysandget-in, or a harness printf). Do not boot the whole application to see one function's output. - Adjust and re-evaluate. Edit the form or the source, re-eval, read again. The cycle is seconds, not a test-suite wait. Let the shape of the data drive the next form.
Hold the loop to pure data wherever the work allows. The pure core is built for this: no clock, no atom, no IO, so a literal input fully determines the output and the value at the prompt is the whole truth.
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.
- 1mo ago First seen · 136 lines · 33 tokens per session scan A ae8cfd0331e6
develop-at-repl is a skill published in the GitHub repository leifericf/agentic-sdk (5 stars, last pushed 1mo ago), licensed MIT. It adds 33 tokens to every session and 1,476 once invoked, about $0.0001 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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