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

Annotations already declare the behavioral profile (readOnlyHint=false, idempotentHint=true, destructiveHint=false, openWorldHint=false), so the bar is lower, but the description contributes nothing on top: it says nothing about whether the previous title is recoverable, whether the rename propagates to other entities, or any authorization requirement. It does not contradict the annotations, but it is a pure name restatement.

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 four-word sentence is maximally front-loaded and wastes no tokens, but at this length it shades into under-specification rather than crisp conciseness given there is a mutation involved. It earns its place only barely.

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 is simple (two required scalar params, no nested objects, no output schema) and the annotations fully cover the safety profile, so an agent can invoke it without the description. However, the description supplies no information about the mutation's effect or scope, leaving the definition minimally viable rather than complete.

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% — song_id and title are both fully documented in the schema, including length constraints. The description adds no additional semantics, so the baseline 3 applies; there is no gap for it to compensate for.

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?

"Change a song's title" restates the tool name rename_song and its title "Rename a song" almost verbatim. It adds no distinguishing detail beyond what the identifier already conveys, and does nothing to separate it from sibling renamers like rename_artist or rename_look.

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 indication of when to use this tool versus the sibling rename_artist/rename_look tools, nor any prerequisite or precondition (e.g., ownership, archived state). An agent must infer all usage context from the name alone.

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