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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful context beyond that: a stated cost of 1 credit and the fact that it reports live vs. pulled status, which matters for interpreting results. It does not cover rate limits or what happens on a not-found app, keeping it below a 5.

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?

Three short clauses: the question it answers, the fields returned, and the cost. The cost is placed last where it belongs, and nothing is repeated from the schema or annotations.

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?

With an output schema present, return values need not be spelled out, and the description nonetheless previews them plus the credit cost. The only gap is not clarifying whether a delisted app returns a status or an error, which an agent would want to know before calling.

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 67% — app_id and storefront are documented, while store is only an enum without prose. The description contributes nothing about parameters, so the schema carries the load. That lands at the baseline 3.

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 frames a specific question (is this app live, or did the store pull it?) and names the resource and the returned fields: name, developer, rating count, first/last seen live. That is a concrete verb+resource that an agent can distinguish from the lookup_domain, lookup_email, lookup_phone siblings in the same family.

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?

The opening question makes the trigger condition clear: use this when you need to verify an app's live status or pull its store metadata. It does not state exclusions or point to alternatives, but the sibling names make resource routing obvious, so context is clear without explicit when-not guidance.

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