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

Annotations already declare readOnlyHint/openWorldHint/destructiveHint, so safety is covered. The description adds real behavioral value by disclosing the return shape ('Top 5 cards with estimated annual cashback/rewards value') in the absence of an output schema, and notes annual_income acts as an eligibility filter.

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?

Purpose is front-loaded in the first sentence, and the Args/Returns blocks are compact. The parenthetical 'which card for ₹40,000 a month?' is borderline verbose but justifies the default choice, so it earns 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, 0% schema coverage, and only generic annotations, the description supplies everything an agent needs: all four parameters documented, the enum values, defaults, units, and the expected return format. Nothing material is missing.

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 0%, so the description carries the full burden and does so well: it gives units for monthly_spend (rupees), enumerates all seven valid primary_category values, states its default and rationale, marks annual_income optional, and defines prefer_no_annual_fee as prioritizing lifetime-free cards.

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+resource+domain: 'Recommend Indian credit cards based on spending pattern.' The 'Indian' qualifier and 'spending pattern' input distinguish it from sibling calculators (find_best_fd, calculate_cagr) and from generic product search.

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?

Explains that monthly_spend alone is a complete question and why primary_category defaults to 'general', which implies usage, but never names an alternative tool or states when NOT to use this versus search_indian_products or compare_products.

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