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

With no annotations, the description carries the burden of behavioral disclosure. It adds value by specifying that the response includes 'all ACF fields' and listing them, but it does not disclose potential errors (e.g., not found), required permissions, or whether the operation is read-only. The word 'Get' implies a safe read, but this is not explicitly stated.

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?

The description is a single, focused sentence that front-loads the primary purpose ('Get a single song') and then enumerates the included fields. Every word adds value, with no fluff or repetition of the tool name.

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?

The tool has no output schema, and the description does double duty by explaining the return content. However, it fails to clarify the relationship between the two optional parameters (id and slug) – specifically, that at least one is needed to identify a song. This ambiguity is a meaningful gap for a retrieval tool.

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?

The schema already documents both parameters (id as 'Song post ID' and slug as 'Song slug'), so the description adds no additional parameter-level semantics. With 100% schema description coverage, the baseline of 3 applies; the description does not need to compensate.

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 clearly states the tool's verb ('Get') and resource ('a single song'), and differentiates it from sibling tools like list_songs by specifying 'single.' It enumerates the specific ACF fields returned (lyrics, quotes, cover art URLs, streaming links, experience data, chapter assignment), making the purpose unmistakable.

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?

The description provides clear context: this tool is for retrieving a single song rather than a list. It implicitly distinguishes from list_songs by emphasizing 'single,' and from get_artist/get_chapter by focusing on the song resource. However, it does not explicitly state when not to use it or mention alternatives, leaving some room for inference.

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