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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds that this is a per-API-key balance lookup, but says nothing about what happens on an invalid or exhausted key, rate limits, or error behavior.

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?

One short sentence with the resource and scope front-loaded and no wasted clauses. It is efficient, though the terseness contributes to the missing usage detail.

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 single-parameter read-only tool with no output schema, the description covers the essential identity of the operation. It still leaves the shape of the result (a numeric balance, a structured object, remaining scans vs. dollars) unspecified, which is the main completeness gap.

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% for the single api_key parameter, so the description must compensate. It partially does by identifying the value as a SiteDoctor API key (a credential rather than an account identifier), but adds no format, sourcing, or error semantics for that key.

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?

States a specific verb and resource ('Check remaining credits') scoped to a 'SiteDoctor API key', which distinguishes it from add_credits and register_free_key without naming them explicitly. Clear enough that an agent would not confuse this with a scan or SEO check tool.

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?

No when-to-use or when-not-to-use guidance, and no mention of alternatives such as add_credits for topping up. The only contextual hint is that it operates on an API key, leaving routing decisions to inference from the tool name.

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