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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the agent knows this is a closed-world safe read. The description adds the useful fact that the tool returns one of three content flavors, but it says nothing about behavior for an unknown slug, auth requirements, or rate limits, so it only modestly exceeds the annotation baseline.

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 compact sentence with the resource front-loaded and the three options enumerated inline; there is no padding. It is a noun fragment rather than a complete statement of action, which slightly weakens front-loading of the tool's operation.

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 carries the burden of describing return content and does so adequately by listing what each mode returns. What is missing is the default behavior when `part` is omitted and any failure-mode information for an invalid slug, for a two-parameter tool with one required field.

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 carry no descriptions there. The description compensates by defining what each value yields (context = the story and theology, info = lyrics, context, style and where to listen), which is genuine added meaning. It still omits relevant detail such as the default value of `part`.

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 enumerates the three distinct payloads it can return (lyrics, context, full info), which is more specific than the bare name and title. It does not, however, name a verb or explicitly distinguish itself from read_doc or browse among the siblings, so it falls short of a 5.

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 statement of when to call read_song versus read_doc, browse, or attend, and no prerequisites or exclusion conditions. The only usage signal is implicit: the parenthetical glosses on each part value hint at which payload to request, but that is parameter guidance rather than tool-selection guidance.

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