With 160 skills installed, Claude Code kept 20 descriptions, and the model found 0 of 3 skills that lost theirs
With Opus 5.5's 1M-token window, Claude Code 2.1.289 held the skill listing to 30,000 characters. Of 160 project skills with 1,000-character descriptions, 20 kept their descriptions (22 of 40, 21 of 80) and every name stayed, but the model invoked 0 of 3 target skills that were listed by name only, against 7 of 7 that still had descriptions. Every skill you install adds a line to the model's…
With Claude Code's 1 million token window, the skill listing was restricted to 30,000 characters. Of the 160 skills, each with 1,000-character descriptions, 20 managed to retain their descriptions (22 of 40, 21 of 80). While the names of all skills were preserved, the model invoked none of the three target skills listed only, as none of them had descriptions.
The skills page in the Claude Code documentation specifies that each skill's name and description are added to the model's context on each turn. When a request is processed, Claude Code uses the description as its sole source of information. The skills page indicates that the character budget for the listing is a percentage of the model's context window, which scales at 1% for a default Opus session.
When the listing exceeds this budget, Claude Code drops the descriptions of the least-used skills first. A warning is logged when the listing overflows, and the character budget can be increased by setting the skillListingBudgetFraction setting or the SLASH_COMMAND_TOOL_CHAR_BUDGET environment variable.
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