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

With no annotations, the description carries the full burden and does disclose the key behavioral fact: identity comes from the MCP connection headers, so no credential parameter is needed. It also previews the payload shape (remaining calls, credits, bundles, purchase instructions), though it stays silent on error behavior for an invalid/exhausted key and does not explicitly label the operation as read-only.

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 sentence that front-loads the primary resource (remaining calls and credits) before the secondary bundle/purchase detail. Dense but every clause adds information an agent needs; only the trailing purchase clause is marginal.

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 zero-parameter read tool with no output schema, the description adequately covers what is returned (free calls, prepaid credits, available bundles, purchase path) and how identity is resolved. It is nearly complete, missing only failure-mode behavior when the key is invalid or credits are exhausted.

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 tool takes zero parameters and the schema is an empty object, so there is nothing for the description to disambiguate. Baseline of 4 applies, and the description correctly implies the caller supplies no arguments.

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 (Show) and resource (remaining free calls and prepaid credits) and scopes it to the API key carried in the MCP connection headers, plus secondary outputs (credit bundles and purchase path). It is unmistakably distinct from the only sibling, read_url, which performs an unrelated fetch operation.

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 — an agent would call this to check quota or decide whether it needs to buy credits — but there is no explicit when-to-use cue, no precondition (e.g. valid key required), and no mention of alternatives or when not to call it.

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