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

Even though readOnlyHint=false and openWorldHint=true already signal the state-changing, world-dependent nature, the description adds meaningful detail: it commits to the exact fetched bytes, uses RFC 3161 timestamps, batches hourly into Bitcoin, and is open to anyone without special permission. No contradiction with 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?

Four short sentences each carry distinct information: the core action and mechanism, the purpose, the honest limitations, and the access/free policy. The most load-bearing detail is front-loaded; nothing is redundant.

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?

The description explains the operation and its purpose well, but with no output schema it does not state what the caller receives or how to reference the seal later. It also lacks error/failure guidance (e.g., a domain without the well-known file), leaving an agent slightly under-informed for a complete invocation lifecycle.

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 input schema already describes both parameters at 100% coverage, including example.com for domain and 'It grants nothing' for requested_by. The tool description adds no further parameter-level nuance, so the baseline score of 3 applies.

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 names a precise verb–resource pair: it 'fetch[es] the A2A agent card a domain publishes at /.well-known/agent-card.json and seal[s] the exact bytes,' then details the nature of the seal (RFC 3161 timestamp, hourly Bitcoin anchoring). It clearly differentiates from sibling tools like verify_certificate and agent_card_history by emphasizing it records claims rather than truth or control.

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 gives clear context for when to use the tool: anyone may seal any public card, it builds a public dated history, and it is free. It also adds negative guidance ('not that any claim is true, nor who controls the domain'), which steers an agent away from using it for verification, though it never names a specific alternative tool.

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