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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description does add useful behavioral context by naming the five dimensions being compared, which matters because there is no output schema, but it says nothing about result volume, pagination, or ordering.

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 tight sentences with zero filler: the first front-loads the action and the comparison dimensions, the second disposes of filter optionality. Nothing repeats and nothing is buried.

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 read-only comparison tool with annotation coverage and an 80%-documented schema, the description is nearly sufficient, and its enumeration of compared attributes partly compensates for the missing output schema. It stops short of stating return shape or result limits, which would matter for an agent planning a call.

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 80%, so the schema already documents chain, category, mcp_only, and max_price_per_1k. The description only adds 'Filters are optional,' which is baseline-level information already implied by the required array; it adds no syntax or edge-case detail 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?

States a specific verb+resource ('Compare APIs in one category') and enumerates the comparison axes (official price, free tier, MCP support, SDK downloads, status). It clearly separates the tool from single-entity siblings like get_api, but it never names an alternative, so sibling differentiation is only implicit.

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?

'Filters are optional' hints that a bare category call is valid, but there is no explicit when-to-use guidance and no mention of alternatives such as get_api for a single API's details or list_api_categories for discovering the required slug. Usage must be inferred.

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