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

Annotations already cover read-only/idempotent/closed-world safety, but the description adds genuinely new behavioral facts: output varies with login state (whether the account can buy now), the underlying payment rails per method (Stripe card, USDC on Tempo, USDC on Base), and a real regional restriction (EU/UK buyers cannot use real money, though credit and diamonds work everywhere). What it does not disclose is any rate/caching behavior or that a region field in the result signals eligibility — that is only gestured at.

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?

It is front-loaded with the scope and contains no filler sentences, but it is a single dense run-on paragraph with deep nested parentheticals (payment rails inside the pack enumeration) that taxes scanning. The regional caveat is buried at the end rather than surfaced where it matters.

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, the description need not enumerate return values, and it correctly focuses on the variability an agent must anticipate (login-dependent buyability, region-dependent real-money eligibility). The one gap is that it never instructs the agent to log in before relying on the buyability fields, leaving an ordering prerequisite implicit.

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 per the baseline there is nothing for the description to disambiguate. The description correctly adds no param-level noise.

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 enumerates the exact contents of the resource (packs with sku/name/USD price, live sales, diamond shop, store credit), which is far more specific than the title's 'List the shop'. It distinguishes itself from buy_pack/send_command by describing what is returned rather than transacted. It loses a point only because the action is framed as a noun phrase ('The whole shop...') rather than a front-loaded verb.

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: it explains that sales are bought 'with sale_id' and diamonds bought 'with the game command shop.buy {sku} through send_command', which implicitly routes the agent here to discover those ids. However, it never explicitly says when to call this versus buy_pack/account, nor any preconditions such as logging in first for the per-account buyability fields.

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