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

With annotations only flagging readOnlyHint=false and idempotentHint=true, the description carries real behavioral weight: nothing is sent to Cairn, the first card is written to private storage and never overwritten, no storage means no save, and the CAIRN_HOME setting constitutes the user's permission. It also states a hard security constraint (public wallet address only, never a key or seed phrase), which is exactly the context annotations cannot convey.

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 purpose is front-loaded in the first clause, then it proceeds cleanly through local behavior, save conditions, and the security caveat. Sentences are dense but nearly every one adds a distinct fact; a small amount of the local/save discussion overlaps and could be tightened.

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 7-parameter tool with a nested object and no output schema, the description covers the full behavioral envelope: what is produced (the agent's own card), where it goes, when it is persisted, and what must never be included. The only minor gap is the exact return shape, which is acceptable given the tool is framed around building a card rather than returning data.

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 all seven parameters (including the nested wallet object and runtime enum) are already documented in structured form. The description echoes the wallet-is-public rule that the schema itself states, adding alignment but no new parameter detail. Baseline 3 is appropriate when the schema does the heavy lifting.

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: 'Build this agent's own Agent Card for A2A participation.' An agent can tell this constructs a card rather than calling, contributing, or saving via other tools. It stops short of explicitly differentiating from the nearby cairn_local_save_card sibling, which also touches card persistence.

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 a usage cue ('Show the card only when needed (for example if payments are enabled later)') and explains the save/no-save condition based on CAIRN_HOME. However, it never names alternative tools (e.g., cairn_local_save_card) or states when a different tool is preferred, so the routing guidance is implied rather than explicit.

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