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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description adds relevant behavioral detail: it enumerates the returned comparison dimensions and notes that apply links are tracked redirects. This goes beyond the annotation baseline without contradicting it.

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 sentences, front-loaded with the core purpose, and each phrase adds value. It lists the detailed fields in a compact list and includes a notable behavior (tracked redirects) without fluff.

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 single-parameter, read-only tool with strong schema coverage and annotations, the description is nearly complete. It covers what data is compared and the one behavioral nuance (tracked apply links). The absence of an output schema or return format is not a significant gap given the tool's straightforward nature.

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 only parameter, ids, is fully described in the schema as 'Card slugs to compare' with minItems=2. The description's 'by id' adds limited extra meaning, and schema coverage is 100%, so the baseline of 3 is appropriate.

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 identifies the tool as producing side-by-side comparison details for multiple cards by ID/slug, listing specific attributes like fees, signup bonus, and earn rates. This distinguishes it from siblings like get_card (single card lookup) and search_cards (discovery).

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 makes clear this is for comparing two or more specific cards by ID, which is a clear usage context. It does not explicitly name alternatives or exclusions, but the scope is well implied by the minItems=2 schema and the nature of the tool.

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