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

Annotations already cover read-only and idempotency, so the description's job is to add behavior, and it does: sort order ('most views first'), pagination mechanics via next_cursor, and the exact fields per row (category, views, unique visitors, free/paid subscribers). Missing only things like rate limits or whether the period is relative to now.

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?

Two dense sentences, front-loaded with the purpose before the return-shape detail. Every clause carries information: scope, sort order, field list, and pagination.

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 carries the return-shape burden and does so fully by enumerating the row fields and the ordering. Combined with 100% schema coverage for the three optional params, an agent has everything needed to call and page through it correctly.

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%, so the baseline is 3, but the description adds semantics beyond the schema: it explains the sort key that makes limit/cursor meaningful and clarifies that the cursor pages through a views-ordered list. It does not restate the enum values or the limit cap, which the schema already handles.

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 ('Where your publication's visitors came from in a period') and scopes it to publication-level traffic sources, which separates it from get_post_traffic and get_audience_insights. The mapped Analytics location ('Analytics > Traffic > Traffic sources') further pins down exactly what is returned.

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 'in a period' phrasing and the publication-level framing imply when this is the right call, but no alternative tool is named and no exclusion is given (e.g. use get_post_traffic for a single post). An agent must infer the boundary from the sibling names alone.

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