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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds value beyond that by disclosing the response contents (usage, limit, reset, a plan-management URL) and by explicitly ruling out mutations ('does not change the plan or purchase credits'), which prevents a plausible agent misread of a billing-adjacent tool.

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?

A single dense sentence that front-loads the account-level data and then the project-scoped extension. Every clause earns its place, though the compound structure makes it slightly harder to parse than two shorter sentences would.

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?

An output schema exists, so return values need detailed description only at a summary level, which the description provides. With one optional parameter and full annotation coverage, the agent has what it needs to call this correctly; only an explicit use-case cue is missing.

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 0%, so the description must carry the parameter's meaning, and it does: 'with a project ID, its keyword and competitor limits' explains both that projectId is optional and what it unlocks. It does not state the expected format (UUID) but the schema enforces that via pattern/format, so the gap is minor.

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 names a specific verb ('Returns') and enumerates the exact resources: API-export access, monthly export usage/limit/reset, and per-project keyword/competitor limits. An agent can tell precisely what comes back. It does not explicitly distinguish itself from get_capabilities, the only sibling with any conceptual overlap, so it stops short of a 5.

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?

Usage is implied (check export quota/reset timing or project limits) but never stated as 'use this when X'. The closing clause 'Does not change the plan or purchase credits' establishes a useful negative boundary so the agent won't expect an upgrade path, but no alternative tool or prerequisite is named.

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