Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well beyond the annotations: it discloses that the return value is a live link that animates in any browser with or without the app, that the artifact is private-by-default until share_vibescape runs, and that a linter will flag music-unreactive output. These are non-obvious behavior traits an agent cannot infer from readOnlyHint/openWorldHint.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the use case and followed by consequences; every sentence carries information. The long parenthetical synonym list ('visualizer, visualization, musicviz, audio-reactive visuals') is slightly bloated but plausibly aids matching.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description correctly compensates by describing the return value (a live link) and its behavior. Combined with the prerequisites and gallery-state caveat, an agent has everything needed to call it and set expectations.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the code/name/author semantics, including the render function signature and uniforms, are already fully documented in the schema. The description adds no parameter-level detail beyond pointing at vibescape_reference for uniforms, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('writes a GLSL vibescape and returns a live link to it'), plus the user intent that triggers it ('music visualiser'). It is clearly distinguishable from siblings like share_vibescape and lint_vibescape, which are named in relation to it.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives an explicit trigger phrase with synonyms, a prerequisite ('call vibescape_reference first'), and the alternative path for visibility ('not in the public gallery until share_vibescape is called'). The agent knows when to use it and what to do before and after.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.