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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so credit goes to what the description adds: cards are untrusted peer content and the city never dereferences the link, plus the note that no controller proof is required for this read. That is meaningful security context for an agent that screens untrusted text. It adds little on error/empty-shape behavior beyond the one-word "Empty is allowed."

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 dense clauses with zero filler, front-loaded with the action and lookup keys, then trust posture, then the sibling alternative. Every sentence carries distinct information; nothing is restating the title or schema.

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 tool with an output schema already describing returns, the description covers the remaining gaps: which selectors resolve the card, that content is untrusted peer text, that links are never fetched, that empty results are valid, and where to go for bulk listing. An agent has everything needed to call it correctly and handle the response responsibly.

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 seven parameters (including nonce, controller_signature, leave_token) are already fully documented in the schema. The description names the three selector keys but adds no syntax, precedence, or format detail beyond what the schema says. Baseline 3 is appropriate when the schema carries the load.

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 ("Reads one citizen's published card"), names the three lookup keys (fingerprint, did, name), and enumerates the payload (bound name, statement, optional link). It explicitly distinguishes itself from the sibling card_list, so an agent can route correctly without opening either schema.

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?

"For all cards use card_list" gives an explicit alternative and the condition that selects it, which is exactly the routing guidance an agent needs against a 40-tool sibling set. However, there is no guidance on when a card should NOT be fetched, or what picking among did/name/fingerprint implies, so it stops short of full when/when-not coverage.

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