Anthropic: Key Highlights of Claude 5.5 in 100 Lines

Anthropic updates its recommendations for creating Claude skills as the 5.5 models approach. The core message is operational: focus on key elements at the top of SKILL.md and manage its length, or risk degraded performance and generic responses.

SKILL.md: prioritize the first 100 lines and stay under 500

Anthropic recommends limiting the SKILL.md file to fewer than 500 lines and placing essential information and instructions within the first 100 lines. When a skill is executed, Claude generally only considers these first 100 lines, making their content crucial. Not all lines in a 500-line SKILL.md hold the same importance. Claude can, for example, use the command “head -100 SKILL.md” to preview the beginning of the file.

Old approaches: risk of wasted tokens and generic outputs

The methods used so far to design skills may be less effective with the new Claude models. They risk leading to unnecessary token consumption or producing generic responses.

Three new rules highlighted for Claude 5.5

Anthropic announces three new rules for creating skills intended for Claude and has updated its best practices. This update concerns the next generation of models, namely Haiku 5.5, Sonnet 5.5, and Opus 5.5. A ready-to-use prompt is also provided to check that existing skills comply with these recommendations.