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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety and network profile is covered. The description adds useful context about what is returned (related apps from the product page) and the country default, but says nothing about pagination, limits, or granularity of results.

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?

Compact and front-loaded: purpose first, then input requirements, then country default, then the sibling pointer. No filler sentences, though the country detail is stated twice (inline and 'Default us').

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 described, and the description covers inputs, default country, and the complementary tool. It is nearly complete for a simple read tool; only the absence of any result-shape or count hint keeps it from a 5.

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 100%, so all four parameters are already documented in the schema, including the id/app_id pairing and the country default. The description largely repeats this, adding no syntax or semantics beyond the schema; baseline 3 is appropriate.

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 ('Returns the related apps shown on the App Store product page'), which is clear and unambiguous. It doesn't explicitly distinguish itself from appstore_search or other appstore_* tools, only framing appstore_app as a complement rather than an alternative.

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?

Gives concrete input guidance (provide either id or app_id) and points to appstore_app for full details, which is a clear context cue. It stops short of saying when NOT to use this tool or how it differs from other discovery tools like appstore_collection or appstore_search.

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