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

Annotations only provide readOnlyHint=false, idempotentHint=false, destructiveHint=false. The description explicitly labels itself as a 'WRITE tool,' and adds the constraint that each product holds at most one iOS + one Android app, which is a critical behavioral constraint. Since annotations lack this detail, the description adds substantial transparency. It could arguably score 5, but there is no mention of whether the operation is reversible or what happens on conflict, leaving a minor gap.

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 description is a single well-structured paragraph of three sentences, each serving a clear purpose: first sentence states the tool's action and contrast with create tool, second adds capacity constraint, third states prerequisites. No filler or repetition.

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?

Given the tool has 4 parameters (100% schema coverage), no output schema, and moderate complexity (linking store versions with constraints), the description succinctly covers the overall purpose, usage boundaries, and prerequisites. There are no missing pieces that would prevent an agent from invoking the tool correctly.

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 the schema already documents all 4 parameters with detailed descriptions (store enum values, ISO country code format, store_id meaning, product_id NOT being a store id). The description does not add additional parameter-level meaning beyond what the schema provides. Baseline 3 is appropriate as the description doesn't detract but also doesn't enhance parameter understanding.

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 clearly states the tool links a second-store version to an existing Sonar product, which is a specific verb-resource combination. It explicitly differentiates this from sonar_create_product by explaining that this tool is for adding an additional store version to an existing product, not for starting a brand-new app.

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 description provides explicit when-to-use guidance ('links the second-store version'), when-not-to-use guidance ('to start tracking a brand-new app, use sonar_create_product instead'), and even specifies prerequisites ('Requires an Indie plan... and an API key with the write scope'). This fully clarifies when to pick this tool over siblings.

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