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

Annotations already declare this is a non-destructive, read-only, closed-world operation, so the safety profile is covered. The description contributes beyond that by saying the response includes pricing and per-site subscription status, which tells the agent this is a site-scoped inventory read rather than a global catalog. It omits whether pricing varies by currency or billing period beyond "monthly."

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?

One sentence, front-loaded with the verb and resource, with the return contents enumerated compactly. No filler or redundancy.

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 one-parameter read tool with full schema coverage and no output schema, this is nearly sufficient: it conveys scope, safety (via annotations), and roughly what comes back. A brief note on the shape of the returned add-on entries or currency formatting is the only meaningful gap.

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 coverage is 100% and the single site parameter is fully documented in-schema, so the baseline of 3 applies. The description's phrase "which ones the site has" reinforces that the call is scoped to one site, but adds no syntax or identifier guidance beyond the schema.

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 pairs the verb "Show" with a specific resource ("monthly add-ons") and states the three things returned: availability, prices, and which add-ons the site currently has. That last clause separates it functionally from add_addon and remove_addon, though neither sibling is named explicitly.

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 read-side listing to consult before calling add_addon or remove_addon, since it reports what is available versus what the site owns. There is no explicit when-to-use or when-not-to-use sentence and no named alternative.

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