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

Annotations already cover read-only, idempotent, non-destructive, and closed-world behavior, so the bar is low. The description nonetheless adds real behavioral context the annotations cannot: estimates derive from publicly reported averages, outputs are ranges (low/mid/high) reflected both pre- and post-royalty, and actual payouts will vary.

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?

Three tight sentences, front-loaded with the core action and output shape. The caveat about averages/actual payouts sits where an agent will read it; the trailing 'Works for any music' is mildly expendable but harmless.

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 usefully discloses the return structure (low/mid/high, pre- and post-royalty) and the accuracy caveat. Combined with annotations and full schema coverage, an agent has enough to invoke it correctly; only explicit alternative-selection guidance 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 description coverage is 100%, so the schema fully documents streams, platform (including "average"), and artist_royalty_rate with its 0-100 range and default. The description restates these at a high level ('a number of streams on a platform, before and after the artist royalty rate') without adding format or edge-case detail, matching the baseline 3 when the schema does the work.

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?

States a specific verb (Estimate) plus the exact resource (streaming payouts) and the output shape (low/mid/high, before and after royalty rate). This is clearly distinguishable from sibling calculators like calculate_cowriter_split or calculate_sync_fee_split, which deal with splits rather than streaming revenue.

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 implies the use case (roughly valuing a number of streams on a platform) and notes it works for any music, but never states when to prefer it over alternatives or any exclusions. No prerequisite or when-not guidance is offered, so the agent must infer context.

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