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

With no annotations provided, the description carries the full behavioral burden and does so well: it says the call is free, charges no credits, logs no usage, and returns a tool error on authentication failure. It also discloses the unverified-email edge case, which is valuable beyond the 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 definition is well structured and front-loads the core purpose and zero-cost behavior. It is somewhat long because it enumerates return fields even though an output schema exists, but the field meanings add useful semantic context rather than pure repetition.

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 one-parameter balance-checking tool with an output schema, the description covers purpose, usage timing, authentication behavior, return-field semantics, and an important edge case. Nothing needed to invoke it correctly appears to be 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 compensate for the lone api_key parameter. It explains the expected `sp-` prefix, the SEARCHPIPE_API_KEY environment variable fallback, and that the explicit parameter takes precedence.

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 and resource: checking the remaining credit balance for the API key. It immediately distinguishes this from search/verify sibling tools by focusing on account balance rather than searching or verification.

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?

It gives clear usage context: poll before batch jobs to avoid 402 insufficient-credits errors, and notes it works even when the account email is not verified. It does not explicitly state when not to use it or name alternatives, but there are no obvious balance-checking alternatives among the siblings.

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