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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, non-destructive, closed-world), so the bar is lower. The description adds genuinely useful context beyond them: 'It loads its own data' tells the agent this render is self-sufficient and needs no prior data call, and it discloses the rendered payload since there is no output schema.

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?

Two short sentences, front-loaded with the verb and resource, then the payload, then the self-loading constraint. No filler and nothing that fails to earn its place.

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 output schema, the description compensates by enumerating what the card renders, and 'It loads its own data' prevents a redundant get_subscriptions call. What is missing is any tie-break against the sibling card tools, but for a zero-required-param renderer the essentials are covered.

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% and the enum parameters (view, views) are documented exhaustively in the schema itself, including when to pick each cut. The tool description adds nothing about parameters, so the baseline 3 applies — the schema does all the work.

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 ('Render') and resource ('subscriptions'), then enumerates the card's contents: total monthly cost, one row per subscription with cadence, next charge date, and New/price-increase flags. The 'Render' verb plus 'It loads its own data' implicitly separates it from the data-fetching sibling get_subscriptions, but it never names that sibling, so differentiation is inferred rather than stated.

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 body offers no explicit when-to-use framing against siblings like get_subscriptions or spending_breakdown; the only guidance is the implicit 'It loads its own data', which tells the agent not to prefetch. The detailed cut-selection advice lives in the view/views parameter descriptions rather than the tool description, leaving tool-level usage implied.

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