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 Creed-Space/METTLE --skill skillgit clone --depth 1 https://github.com/Creed-Space/METTLEWrote 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/creed-space/mettle/skill)<a href="https://agentmods.dev/skills/creed-space/mettle/skill"><img src="https://agentmods.dev/badge/skills/creed-space/mettle/skill/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/creed-space/mettle/skill"><img src="https://agentmods.dev/badge/skills/creed-space/mettle/skill.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 | $0.00753 |
| Opus 5.5 | $0.00013 | $0.00301 |
| Sonnet 5.5 | $0.00007 | $0.00151 |
| Haiku 4.5 | $0.00003 | $0.00075 |
Grade A, and why
mettle 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 24d 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 — 73 lines — stays where its author put it; the contents beside it link to each section on GitHub.
METTLE Screening
METTLE runs machine-oriented reverse-CAPTCHA challenges:
verifiedmeans the session met the configured challenge policy;- qualifying public quick sessions may receive a signed Bronze or Silver badge, which relying services check with the issuer;
- the authenticated suite API defines Bronze through Platinum as complete suite ranges, but under the current suite policy Suites 6 through 9 and 11 are not credential-eligible, so it issues Bronze at most today;
- badges and credentials expire and may be revoked;
- public entity identifiers remain explicitly self-asserted.
Interactive API Flow
- Call
mettle_start_sessionand retain the returnedsession_id. The MCP host keeps the session bearer outside model-visible content. - Answer each challenge with
mettle_answer_challenge. - Read the result, and the signed badge if one was issued, with
mettle_get_result. A tier without a badge is not a credential.
The auto-solve tool was removed. Never route a reference solver into a live session.
Do not supply or request a session_token tool argument. Direct REST clients have a
different responsibility and must retain the bearer returned by the API.
Mode Selection and Current Limits
Use the three quick tools above for a complete Bronze or Silver screening flow.
Use mettle_list_suites, mettle_start_v2_session, mettle_verify_suite, and
mettle_get_v2_result for authenticated single-shot suites. Use
mettle_submit_round and mettle_get_round_feedback for novel-reasoning.
Use mettle_get_session to inspect either profile and
mettle_cancel_session to cancel an authenticated session.
If a tool reports an unknown or expired quick session, the host no longer has the hidden bearer. Do not guess it. Start a new session only if consuming another session and quota is acceptable.
Quick result reads are repeatable while the hidden caller capability remains in the MCP vault. Prefer structured content over parsing compatibility text. Follow the returned actions rather than guessing call order.
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.
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.
- 24d ago Changed · +5 lines · +1 tokens per session b4b31ca12eaa
- 1mo ago Changed · +21 lines 1efe827b2210
- 1mo ago First seen · 47 lines · 32 tokens per session scan A 3f4341179102
mettle is a skill published in the GitHub repository Creed-Space/METTLE (0 stars, last pushed yesterday), licensed Apache-2.0. It adds 33 tokens to every session and 753 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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