compare_periods

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

The description discloses useful behavior beyond the annotations: rows are sorted by click change, biggest losses are at the bottom, biggest gains at the top, and the default comparison is the last 28 days against the 28 before them. It leaves exact return fields unstated, but the read-only and idempotent annotations cover the safety profile.

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?

Four sentences, each earning its place: what the tool computes, what questions it answers, the default comparison window, and row ordering. The most important information is front-loaded with no filler.

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 six-parameter tool with no output schema, the description covers selection criteria, default behavior, dimensions, and output ordering. It would benefit from naming the exact returned metrics, but the schema and annotations already handle parameter types, requiredness, and safety, so the definition is largely complete.

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 high, so the baseline is 3. The description adds the meaningful default-window relationship that the schema's `days` property leaves implicit: the last 28 days are compared against the 28 days before them. Its dimension list mostly restates the schema enum, but the extra context justifies a 4.

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 identifies a concrete resource and outcome: two equal date windows compared with precomputed deltas per query, page, country, or device. It also maps the tool to user intents like 'what changed' and 'are we up or down', making it easy to distinguish from the sibling analytics tools.

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 phrase 'This is the tool for' plus explicit example questions gives strong when-to-use guidance. It does not name alternatives or state when not to use it, so it stops short of full exclusion guidance.

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