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

Annotations declare readOnlyHint=false, destructiveHint=false and idempotentHint=false, so the safety profile is already carried. The description adds genuinely non-structured context: the filter is applied at read time, history is retroactively recomputed, and the operations view reports how many visitors were excluded so the change stays auditable. It stops short of describing failure modes or what happens to a visitor_id that no longer exists.

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?

Front-loaded with the action and its consequence, and every sentence carries information, but the 'one of us' phrasing and the aside about inflated read numbers add rhetorical length that a tighter definition could drop.

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?

No output schema is needed since the description explains the recomputation effect and where the exclusion count surfaces. For a two-parameter mutation whose annotations already cover safety, the description covers effect, scope, undo and id source completely.

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 both parameters are documented in-schema, so baseline is 3; the description adds marginal value by restating the undo semantics of internal=false and pointing to list_sessions as the source of visitor_id, though both points largely duplicate the schema descriptions.

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 ('mark one visiting device as internal') plus its exact effect: excluded from views, visitor counts and the funnel, recomputed at read time. An agent can tell this apart from siblings like set_internal or set_visibility without opening a 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?

Gives explicit when-to-use cases (the user's own phone and laptop, colleagues, demo opens) and the undo path ('pass internal=false'). It also names the source for the required id: 'Get visitor_id from list_sessions'. Nothing is left to inference.

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