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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is known. The description adds that the tool shows 'SC and GA metrics' with percentage changes, which is useful but does not disclose additional behavioral traits (e.g., pagination, response format, or handling of missing data). It is adequate but does not significantly extend beyond the 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?

The description is two sentences with no redundancy. The purpose is stated first, followed by practical use cases. Every word 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 comparison tool with 5 parameters and no output schema, the description covers the core purpose and the metrics shown. The only gap is not explaining what 'SC' and 'GA' stand for, which might be domain-specific but is a minor omission. Overall, the agent has enough information to call the tool 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 description coverage is 100%, so the schema already documents all five parameters. The description does not add meaning beyond the schema, such as explaining what 'SC' and 'GA' refer to or detailing how the date ranges interact. It relies on the schema for parameter understanding, which is acceptable.

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 states a specific verb ('Compare'), a resource ('analytics periods'), and the scope (two date periods for a project). It also distinguishes itself from the sibling get_project_analytics by explicitly mentioning period-over-period comparison with percentage changes. This is clear and unambiguous.

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 provides explicit use cases: 'Use for week-over-week, month-over-month comparisons, measuring campaign impact, tracking growth/decline.' It gives clear context for when to apply the tool. It does not name an alternative or state when not to use it, but the guidance is sufficient for an agent to decide.

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