Mistral Medium 3.5 (reasoning)
Mistral · proprietary · writing benchmark
The short version
Mistral Medium 3.5 (reasoning) sits at #97 of 130 on ToneBench, toward the value end of the board, with a writing Elo of 1158 and an overall score of 73.0 out of 100. We measured it by having it write all 9 of our real YouTube scripts, five times each, then scoring every draft blind against our own finished versions. Here is how it shook out.
Inside Mistral, this is the strongest writer we tested. It edges out the other 3 Mistral configs on the board, so if you're staying in this family for voice work, this is the one to reach for.
Among proprietary models, it comes in 72nd of 83. That ranking is against the stronger half of the board: closed models still set the pace on voice fidelity here.
What it does best is Visual Cues: it ranks 82nd on that dimension at 75.3, above the board average. Its softer spot is Writing Craft (73.7, 106th), which is the thing to watch if that metric matters most for your use.
It was uneven across the 9 scripts. Its best run was the opinion / warning explainer (76.4) and its weakest was the personal technical walkthrough / agentic workflow case study (70.3), a spread of about 6 points. Worth knowing if your writing skews toward one of those formats.
On cost, it runs about $0.149/task (estimated). DeepSeek V4 Flash (native chat alias) scores higher for less money, at $0.002/task, so on pure value this config is not the frontier.
Skill profile
The shape is the story: the further a corner reaches, the stronger that dimension. Biggest edge over the board: Visual Cues (+0.7); furthest behind: Flow & Emotion (-7.2).
Per-metric scores
Nine writing dimensions, each scored 0–100 and blended by the editorial weight shown. Rank is against all 130 current-ranked models. The thick bar is this model; the thin lines above and below are the current field's best model (darker) and average (lighter) on the same scale. The small ± number is its run-to-run variation.
Per-article scores
The same 9 real scripts every current-ranked model writes, scored individually. Different formats stress different skills.
Consistency: run-to-run variability
Every cell on this page is the mean of 5 independent runs per script; the ± numbers are the run-to-run standard deviation. Overall, Mistral Medium 3.5 (reasoning) varies by ± 4.7 points between runs versus a board median of ± 3.8, so it is about as repeatable as the typical model on the board.
Its most volatile dimension is Tone & Voice (± 3.3 vs a board median of ± 2.2): two runs of the same brief can land visibly different tone & voice scores.
| Metric | This model | Board median | Verdict |
|---|---|---|---|
| Tone & Voice ? | 75.5 ± 3.3 | ± 2.2 | swingier than most |
| Writing Craft ? | 73.7 ± 4.2 | ± 2.0 | swingier than most |
| Substance & Value ? | 73.8 ± 4.7 | ± 2.6 | swingier than most |
| Flow & Emotion ? | 67.2 ± 5.7 | ± 2.6 | swingier than most |
| YouTube Structure ? | 72.3 ± 4.6 | ± 3.6 | typical |
| Hook ? | 80.8 ± 3.9 | ± 3.0 | typical |
| Length Discipline ? | 62.6 ± 20.3 | ± 8.6 | swingier than most |
| Anti-Slop ? | 77.4 ± 4.8 | ± 2.6 | swingier than most |
| Visual Cues ? | 75.3 ± 7.5 | ± 4.7 | swingier than most |
Measured, not modeled
Numbers we log on every run and rarely talk about. None of these affect the writing scores; cost and latency are informational.
What each judge scored it
The published overall of 73.0 is the consensus of three family-disjoint judges scoring the same 45 stored drafts blind with the identical rubric. The highest and lowest judge differ by 12.0 points on its overall. A typical amount of judge disagreement for this board. How the panel works: methodology.
How we ran Mistral Medium 3.5 (reasoning)
- Accessed viaOpenRouter · model page ↗
- Exact model / route id
mistralai/mistral-medium-3-5atreasoning_effort: high - Audited route overrideOpenRouter ·
mistralai/mistral-medium-3-5forautomated_video_workflow(Task-7 exact OpenRouter endpoint pin mistral) - Generations5 independent runs × 9 scripts = 45 drafts, stored immutably after generation
- Run dates2026-07-29 → 2026-08-11
- Judges3-judge panel: Claude Opus 5, high effort (Anthropic) + DeepSeek V4 Flash (OpenRouter) + GPT-5.6 Sol, medium reasoning (Codex CLI): every draft scored independently by all three with the identical rubric, blind to model identity, evidence quotes required before each metric score; published score = per-metric consensus mean, verified with a Bradley-Terry refit (methodology)
- Samplingprovider-default sampling, no fine-tuning, no system-prompt changes; every current-ranked model gets the identical brief, style contract and research packet
- What stays privatethe exact rubric and any non-public reference material; source-publication timing is disclosed for exceptions (why)
Frequently asked questions
How good is Mistral Medium 3.5 (reasoning) at writing?
On ToneBench it ranks #97 of 130 with a writing Elo of 1158 and an overall score of 73.0/100. That score comes from writing our 9 real YouTube scripts five times each and scoring every draft blind against our own finished versions across nine writing dimensions.
Is Mistral Medium 3.5 (reasoning) the best Mistral model for writing?
Yes. Among the Mistral configs we tested, Mistral Medium 3.5 (reasoning) is the strongest writer on the board.
Is Mistral Medium 3.5 (reasoning) good value for the money?
It costs about $0.149/task (estimated). DeepSeek V4 Flash (native chat alias) scores higher for less, so it is not the value pick.
What are Mistral Medium 3.5 (reasoning)'s strengths and weaknesses?
Its strongest dimension is Visual Cues (82nd on the board, 75.3). Its weakest is Writing Craft (106th on the board, 73.7). The full nine-metric breakdown is on this page.
Does Mistral Medium 3.5 (reasoning) write some formats better than others?
Yes. Its best of our 9 scripts was the opinion / warning explainer (76.4) and its weakest was the personal technical walkthrough / agentic workflow case study (70.3).
How consistent is Mistral Medium 3.5 (reasoning) between runs?
We run every script 5 times. Mistral Medium 3.5 (reasoning)'s overall score varies by about ±4.7 points between runs, versus a board median of ±3.8. That is typical consistency for this board. The full per-metric variability table is on this page.
How was Mistral Medium 3.5 (reasoning) evaluated?
Via OpenRouter using the exact model/route id mistralai/mistral-medium-3-5 at reasoning_effort high, run on 2026-07-29. 5 runs per script, provider-default sampling, no fine-tuning; every draft scored blind with a fixed rubric by a three-family judge panel. Full details in the 'How we ran it' section and the methodology.
Is Mistral Medium 3.5 (reasoning) open source?
No, it is a proprietary (closed-weights) model. Among proprietary models it ranks 72nd of 83 for writing.