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

Adds substantial context beyond readOnlyHint=true: it discloses the authentication prerequisite, the shape of the returned payload, and a security constraint that an identifier is never returned (SEC-PM-006). That is meaningful behavioral disclosure for a read tool, though it omits error/not-found behavior.

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?

Purpose, return contents, and access protocol are front-loaded and ordered logically. The opaque SEC-PM-006 reference is the only bit of noise, but it does not bloat the description.

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 correctly takes on the burden of describing what is returned, and it covers the auth prerequisite that an agent would otherwise trip over. Missing only failure/error semantics for a nonexistent ID.

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 single 'id' parameter is fully documented there (including the 24-hex pattern). The description restates 'by ID' but adds no format, constraint, or example beyond the schema, so the baseline 3 applies.

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 ('Get a Circle by ID') and even enumerates the returned payload (members, channel presence booleans). It implicitly separates itself from list_circles via 'by ID', but does not name any sibling explicitly.

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?

Provides a real usage gate – requires a Proof account, must authenticate the client first, and start_login does not cover it – which is helpful. However it says nothing about when to prefer this over list_circles, list_circle_members, or get_circle siblings, so selection guidance is only implied by the 'by ID' framing.

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