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

Annotations already declare readOnlyHint, openWorldHint, and non-destructive behavior. The description adds significant non-annotation context: it discloses that each call costs $0.009 USDC via x402, lists supported chains, explains automatic payment for x402 MCP clients, and offers a free sample. This is valuable behavioral disclosure beyond the structured annotations.

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 front-loaded with purpose and return fields, then default port, use cases, payment mechanics, and a free sample. It is slightly dense but every sentence adds useful information for an agent deciding to invoke the tool.

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?

Given no output schema, the description lists the returned fields (valid, days_remaining, issuer, dates, SANs, fingerprint, protocol), which is essential. It also covers payment and usage context. It is complete for a simple read-only check tool, though it could mention error or timeout behavior.

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%, so the schema already fully documents both parameters. The description repeats the default port 443 and gives an example input, but adds no new syntax or format meaning beyond what the schema provides.

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 states a specific verb and resource: 'Inspect SSL/TLS certificate for any domain.' It clearly distinguishes the tool from generic domain or DNS siblings by focusing on certificate inspection, but it does not explicitly name an alternative tool for comparison.

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?

It provides clear use cases: 'certificate expiry monitoring, security audits, or HTTPS verification.' This tells the agent when to use it, but it does not specify when to prefer alternatives such as whois or domain_check.

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