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

Annotations already declare readOnly, idempotent, non-destructive, so the safety bar is low. The description adds genuinely useful behavior beyond that: it returns null when a card was never published, unpublished, or retired, which an agent needs to handle correctly.

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, front-loading the action and following with the return-value caveat. No wasted text.

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, the description covers the key return behavior (card data or null), which is the main thing an agent needs. It could say more about card contents, but for a single-param lookup this is close to complete.

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 100% and the schema itself already explains agentCardId's origin ('as returned by search_directory's agentCardId field'). The description adds nothing beyond this, so 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?

States a specific verb and resource ('Fetches a single agent's published, public agent-card data by its agent card id'), which is clearly distinct from directory search or registration siblings. It does not explicitly name an alternative tool, but the scoping ('single', 'by id') makes the distinction from batch/search tools evident.

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 description implies usage (look up one card once you have its id, e.g. from search_directory) and explains the null outcome, but never explicitly states when to use this versus search_directory or find_verified_agent. Guidance is implied rather than spelled out.

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