The Claude skill description character limit is 1024 characters. That is the hard cap on the description field in your SKILL.md frontmatter, and the validator enforces it. Anthropic states it plainly in the Agent Skills best-practices doc. The companion name field caps at 64 characters. Those two numbers are the whole format contract for the metadata block. So if you landed here because something rejected your skill, this page is the answer.
The Claude skill description character limit, and the name limit
A SKILL.md frontmatter requires two fields, and each has a fixed maximum.
description: maximum 1024 characters, must be non-empty, no XML tags. This is the Claude skill description length cap.
name: maximum 64 characters, lowercase letters, numbers, and hyphens only, no XML tags, and it cannot contain the reserved words anthropic or claude. That is the claude skill name length rule in full.
Both limits come straight from the best-practices page, which lists them under YAML frontmatter requirements and repeats them in its technical notes. The skill md description limit is not a soft guideline. It is a validation rule, and a description over 1024 characters is an invalid skill, full stop.
What the body limit actually is
The SKILL.md body is different. It has guidance, not a hard cap. Anthropic recommends keeping it under 500 lines for performance, and the Claude Code docs repeat the same number as a tip. Past that, you are meant to split content into separate files and let Claude load them only when a task needs them. Nothing fails validation at line 501. The body just gets slower and heavier in context, which defeats the point of a skill that is supposed to stay cheap until used.
So the claude skill character limit story has two layers. The frontmatter has real numeric ceilings, 1024 and 64. The body has a recommended ceiling of 500 lines that you should respect but will not be blocked by.
What happens if you exceed the cap
Go over 1024 characters in the description and the skill is invalid. Depending on where you publish, that surfaces as a validation error at authoring time, or as a load failure when the runtime parses the file. Either way the skill never becomes available, and there is no silent truncation of the stored field at 1024.
There is a second number that trips people up, and it is worth separating cleanly. Claude Code applies a listing truncation that has nothing to do with the format cap. When skill metadata loads into context so Claude can decide what to use, the combined description plus when_to_use text for each skill is capped at 1,536 characters in that listing, and the budget across all skills scales with the model's context window. Got a lot of skills? The descriptions of the ones you invoke least get shortened or dropped first to fit the budget. Anthropic documents this in the Claude Code skills reference, and you can check it with /doctor.
The practical reading: 1024 is the format ceiling per field. 1,536 is a per-entry listing ceiling for description plus when_to_use combined. The shared budget is what actually clips your text in a crowded session. None of these are numbers you want to be writing up against.
A good description sits well under the cap
Here is the take that matters more than the number. A description that approaches 1024 characters is almost always a bad description. The field has one job: tell Claude what the skill does and when to use it, so the model can pick it out of a hundred others. That job wants a tight sentence or two with concrete trigger terms, written in third person, key use case first. Something like "Extract text and tables from PDF files, fill forms, merge documents. Use when the user mentions PDFs, forms, or document extraction" runs about 110 characters and does the whole job.
If you are bumping the limit, you are probably stuffing implementation detail into the description. Move it into the body, where it belongs and where progressive disclosure keeps it free until needed. The cap is a backstop you should never feel. For the full method of writing one that earns its tokens, see how to write a SKILL.md description.
Writing these by hand and counting characters gets old fast. Knack turns a short interview into a valid SKILL.md folder with the name and description already inside the limits, so the format contract is handled and you spend your attention on the instructions Claude actually runs.
Keep the name short, keep the description specific and under a couple hundred characters in practice, and the 1024 ceiling stays a thing you read about rather than a thing you hit.