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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds real context beyond that: the listing is scoped to the apps the current key can access, rows are per-platform rather than per-app, and each row carries subscriber counts and a ready-to-send flag. Pagination and ordering behavior are not disclosed, keeping it short of 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 tight sentences with no filler: purpose first, row shape second, how to reuse the identifiers third. Every sentence adds information an agent needs.

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 no input parameters and no output schema, the description carries the full burden and does so: it explains scope (this key), entry granularity, key identifying fields, and the extra data fields returned. Nothing essential for a correct first call is 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?

The tool takes zero parameters, so the baseline is 4. The mention of productId and platforms "all" refers to arguments for downstream tools, not to this schema, but it usefully explains how this tool's output keys map to other calls.

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 ("Lists the apps this key can use") and immediately clarifies the unit of each row: one platform of an app, grouped by productId and productName. That granularity detail is exactly what distinguishes this discovery endpoint from siblings like get_account or get_setup.

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 clear forward-looking usage guidance — pass productId or platforms "all" to other tools to act on every platform at once — which tells the agent why to call this first. It does not name a competing sibling or state when not to use it, so no explicit alternative routing.

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