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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the description doesn't need to restate safety. It adds useful return behavior by listing the specific computed metrics and noting the verdict is deterministic, which is especially valuable given there is no output schema.

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 concise sentences with no filler. The core comparison behavior and constraint are front-loaded, followed by the returned fields and the use case, making it easy to parse quickly.

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 simple one-parameter, read-only tool, the description covers the key returned fields and the intended use case. It does not define 'strongest transparency signal' or describe error behavior, but the schema constrains input bounds and annotations cover safety, so the description is reasonably 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?

The input schema has 100% coverage with a clear description for the single 'slugs' parameter, including min/max items. The description repeats '2-5' and 'by slug' without adding extra semantic detail such as slug format, source, or examples, so it stays at the baseline for full schema coverage.

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 a specific verb and resource: side-by-side comparison of charities by slug. It enumerates the exact returned data and includes a deterministic verdict, and the use case 'choose between named charities' distinguishes it from sibling tools like search or verify.

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 says 'Use this when the user wants to choose between named charities,' giving a clear when-to-use trigger. It does not explicitly name alternatives or when-not-to-use conditions, but the stated use case is sufficient to route an agent correctly.

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