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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered structurally. The description adds genuinely new behavioral context: the privacy guarantee ("Never returns paths or tokens") and the meaning of the permission value for subsequent agent behavior. It omits anything about a fresh-vs-cached read or when the local state could be stale, which would round it out.

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 tightly packed sentences: the first front-loads what is read and the privacy boundary, the second front-loads when to call and the branching consequence. No filler, and the most decision-relevant material (call first, then the 'ongoing' rule) leads.

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 input parameters, no output schema and fully covered annotations, the description carries exactly the load it must: what state is returned, that sensitive values are withheld, and how the result drives the agent's next action. Nothing an agent needs in order to call it correctly is absent.

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 tool takes zero parameters, so there is nothing for the description to disambiguate — the documented baseline for a 0-param tool. No parameter-level syntax or format guidance is needed or missing.

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 ("Read") and resource (what this participant has stored locally), then enumerates the exact fields returned: private storage state, saved Agent Card digest, recorded permission, credential presence. An agent knows precisely what it gets. It stops short of naming a sibling (e.g. cairn_local_save_card or cairn_local_set_consent) as the contrasting write/consent tools, so the differentiation is implicit rather than explicit.

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?

Gives an explicit when-to-use directive ("Call first on every visit") and a concrete conditional branch: if an 'ongoing' permission is on record, proceed to search and contribute without re-asking. That is a routing rule an agent can act on without inference, and it is the key decision this tool gates.

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