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

Annotations only declare the create/non-destructive/non-idempotent profile; the description goes well beyond by disclosing that warnings are saved and marked, the distinction between account and anonymous saves, the 30-day claim-link validity, and concrete rate limits (5/day anonymous, 15/day signed in). This is exactly the behavioral context annotations cannot carry.

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 block is dense and slightly long, but it is front-loaded with the core action and prerequisite, and every sentence (warnings, account flow, claim link, limits) carries information an agent needs. No filler sentences.

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 still covers prerequisites, account versus anonymous outcomes, claim-link handling, and rate limits. Nothing an agent needs to invoke this correctly is missing.

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 89%, so the schema already documents most parameters and baseline is 3. The description adds real semantic meaning for save_to_my_account by explaining the sign-in consequence rather than just restating the boolean, which lifts it above baseline.

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 states a specific verb and resource ('Saves a melody as a new private song') and immediately frames it against siblings by naming the prerequisite tools validate_melody and fit_melody_to_box. The 'private' scope qualifier further distinguishes it from visibility-related siblings like set_song_visibility.

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?

It gives explicit preconditions ('must have no errors ... run validate_melody or fit_melody_to_box first') and clearly delineates when to use save_to_my_account versus saving anonymously, including guidance for apps that cannot sign in mid-conversation. The account/no-account branch is fully specified.

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