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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safe-read profile is covered. The description adds useful scope detail by defining what each reading mode yields, but says nothing about failure behavior for an invalid slug or about the size/shape of the returned payload beyond the output schema's implicit coverage.

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?

A single sentence with zero filler that front-loads the primary option (lyrics) and then the two alternatives. The nested parentheticals are slightly heavy but every clause maps directly to a distinct enum value, so nothing is wasted.

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 an output schema present, return values need not be explained, and the description correctly focuses on distinguishing the three modes. Combined with annotations covering the read-only nature, this is near-complete for a two-parameter fetch tool; only the missing routing guidance against sibling tools holds it back.

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 only 50%: the slug parameter is documented in the schema, but the `part` enum values appear with no descriptions. The description compensates by glossing each value ('lyrics' = the lyrics, 'context' = story and theology, 'info' = lyrics, context, style and where to listen), which is real meaning added beyond the raw enum list.

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?

The description names the resource (a song) and precisely enumerates the three content variants it can return (lyrics, context, full info), which is far more informative than the title 'Read a song' alone. It lacks an explicit verb and any differentiation from siblings like search or browse, but the resource and payload scope are unambiguous.

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?

There is no when-to-use guidance, no prerequisites, and no mention of alternatives such as search or browse for finding a song. An agent must infer from the name that this is the terminal fetch step after obtaining a slug, and nothing tells it what to do if it lacks a slug.

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