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

Annotations cover the safety profile (readOnly, non-destructive), but the description adds genuinely useful behavior: the Advanced-Plan requirement and the specific failure mode (plan error), plus the Cotlet API key requirement. It also discloses ordering ('biggest first') and that total_downloads is the row sum, which annotations cannot convey.

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?

Information is front-loaded and useful, but the first two sentences overlap heavily ('Downloads split by country, listening app...' followed by 'Splits a show's downloads... by country, listening app...'), and the Advanced-Plan requirement is stated twice within a short block, which pads the definition.

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 helpfully explains the return shape (one row per split value, biggest first, total_downloads as the sum) and covers auth, plan gating, and read-only status. It is nearly complete; only cross-referencing to sibling stats tools is absent.

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 baseline is 3. The description adds a small amount by equating the 'listening app' dimension with the user_agent parameter value, but otherwise adds no syntax or format detail beyond the schema.

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 and resource ('Splits a show's downloads for a date range') and names the exact dimension options (country, listening app, publishing destination), which pins it apart from aggregate siblings like get_show_stats. An agent can identify the tool and its output shape without opening the schema.

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 Advanced-Plan gating is clearly stated, which is a real precondition. However, it gives no explicit guidance on when to prefer this over libsyn_get_show_stats or libsyn_get_episode_stats, leaving the choice to inference from the resource names.

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