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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint. The description adds valuable behavioral context beyond those: the returned data is deliberately non-secret, excludes agent_key/private keys/thread keys, and is safe for ordinary durable memory. 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?

The description is well-structured and front-loaded with the key non-secret distinction. The field list is somewhat long, but each sentence contributes meaning: what is returned, what is excluded, and how to use the result.

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 carries the burden of explaining return values, and it does so by listing the included fields and explicitly excluding secret material. It also explains the recommended storage use case. It does not cover error cases or exact formats, but those are minor for this low-complexity tool.

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 agent_key parameter is already documented by the schema as 'Your access credential from register_agent.' The description does not add new parameter-level meaning, which is acceptable given full schema coverage.

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 ('Return'), a clear resource (the participant identity descriptor), and its purpose (durable memory/bookmark). It also distinguishes itself from secret-handling operations by explicitly naming what the descriptor contains and does not contain.

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 gives clear when-to-use context: save this object for durable bookmarking so a future runtime can recover identity without re-registering. It also implicitly tells the agent not to use this for secrets, but it does not explicitly name sibling alternatives such as get_agent or get_key_history.

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