Get subscriber growth sources

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

Annotations already cover readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is established. The description adds behavioral context by explaining the output is ranked and windowed, and cross-references get_analytics for data equivalence. No contradiction with annotations.

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 sentences with no wasted words. The first states the tool's purpose and ranking behavior; the second explains its relationship to get_analytics and why it exists. All content earns its place.

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?

For a read-only query with no required parameters, a fully documented schema, and strong annotations, the description is sufficient for correct invocation. The lack of an output schema is partly mitigated by the get_analytics cross-reference, though specific return fields or source categories are not enumerated.

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?

The input schema fully documents all three parameters with formats, defaults, and descriptions, so schema coverage is 100%. The description's mention of a 'window' loosely maps to the date parameters but does not add new technical meaning 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?

The description clearly states what the tool returns: where new subscribers came from in a window, ranked by source. It also distinguishes itself from the sibling get_analytics by noting it is the same growth_sources report kept as a dedicated tool for a common question.

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 explicitly names get_analytics as the alternative and explains the relationship: this tool exposes the growth_sources report directly. It does not spell out a strict 'use this when X, use get_analytics when Y' rule, but the context makes the appropriate choice clear.

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