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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true. The description adds meaningful context: 'No browser, no proxies, no login' and pricing ($0.01/call, x402). These details go beyond annotations and set expectations for execution environment and cost, without contradicting the read-only nature.

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?

The description is a single, information-dense sentence that front-loads the core functionality and includes a brief pricing note. No filler or redundancy; every word contributes to understanding what the tool does and its constraints.

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 tool with 2 params and no output schema, the description adequately covers the main use case, diff input format (mentioning 'previously-seen stack'), and key operational traits (no browser/proxies). It doesn't describe the output structure, but the phrase 'exactly what was added or removed' gives enough of a picture for simple usage.

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 schema itself explains the 'items' format (bare or diff form) and 'maxConcurrency'. The description adds no new parameter syntax beyond what the schema provides, so the baseline 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 states the tool's function: 'Detect a website's current technologies ... and diff it against a previously-seen stack you supply, so you get exactly what was added or removed.' This uses a specific verb (detect and diff) and resource (website stack), and distinguishes from the sibling 'tech-stack-detector' by emphasizing the comparison against a supplied baseline.

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 phrase 'previously-seen stack you supply' clearly indicates this tool is for change detection when a prior stack is known, implicitly differentiating from simpler detection tools. It does not explicitly name alternatives or state 'when not to use', but the context is strong and the pricing note adds practical guidance.

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