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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description adds meaningful context beyond that: it names what is returned (prepaid credits, Pro Reports allowance, plans, Pro status) and explains key-dependent behavior, including that order_title_search pays from credits with a key and returns a checkout link without one. It stops short of describing response format or rate limits, so it is strong but not exhaustive.

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 core capability (credits, plans, Pro status) is front-loaded in the first sentence, with supporting context following. The parenthetical detailing the Bearer token format (hd_live_...) is slightly extraneous for an agent that cannot manipulate the connection auth, but overall it is tight and purposeful.

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-only tool with no output schema, the description supplies enough: it enumerates the returned information and explains the key/no-key behavioral split, including the fallback guidance when no key is present. A precise response shape would complete it, but nothing critical is missing for correct invocation.

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 fully covered (trivially at 100%), so the baseline of 4 applies. The description correctly implies no inputs are needed, though it does not explicitly confirm that.

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: reports credits left (prepaid and Pro Reports allowance), current plans, and Pro status for the account tied to the API key on this connection. This is clearly distinguishable from siblings like buy_plan or order_title_search, since it inspects account state rather than performing a purchase or lookup.

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 rather than stated: an agent can infer this is the tool for checking account standing, and the note that order_title_search draws from these credits hints at a pre-purchase check. However, it never explicitly says when to call this versus alternatives like buy_plan or get_terms, nor does it give a when-not condition.

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