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

With no annotations, the description carries the full burden. It does disclose two behavioral facts an agent needs: the operation is read-only, and it requires an API key. However, it says nothing about rate limits, whether the window is fixed at 7 days or configurable, or the response shape.

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?

One dense sentence front-loads the purpose and content list before the trailing caveats. It is compact and wastes little, though the trailing fragments 'Read-only. Needs a key.' are slightly clipped rather than integrated.

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 zero-parameter, read-only report with no output schema, the description enumerates what the report contains, which is enough for an agent to decide whether to call it. Auth and safety are covered; only output format and window flexibility are left unstated.

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 the baseline is 4; there is nothing for the description to disambiguate. The schema description coverage is trivially 100% given the empty properties object.

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 deliverable (a weekly summary report) and enumerates its content — sign-in domains, sessions opened, blocked attempts, per bot — which implicitly separates it from raw-event siblings like audit_log and session_fetch. It does not explicitly name an alternative, so it falls just short of a 5.

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?

There is no guidance on when to call this versus audit_log (raw events) or session_fetch (session detail). The only usage-adjacent statement is the precondition 'Needs a key', which is an auth note rather than selection advice.

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