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

Annotations already cover the safety profile (readOnlyHint true, destructiveHint false, openWorldHint true). The description adds meaningful context beyond them: with no output schema, it discloses what the response contains (pages and countries of current visitors) and the underlying endpoint. It omits any note on freshness/caching or rate limits, hence not a 5.

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 compact sentences that are front-loaded with the core meaning and append the endpoint for reference. No filler or redundancy.

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 two-parameter read-only tool with no output schema, the description covers purpose, returned content, and the lookback concept, which is close to sufficient. It stops short of stating prerequisites (a domain_id must be obtained via pirsch_list_domains) or how the real-time data relates to the other statistics tools.

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 schema already documents both `start` (1-3600, default 600) and `domain_id` fully. The description only alludes to the lookback window via 'in the past n seconds' and adds no format, default, or cross-reference detail, so the baseline of 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+resource ('Visitors on the site right now') and distinguishes the tool from historical siblings with the real-time framing. It also names the returned facets (pages, countries), so an agent can tell it apart from pirsch_get_totals or pirsch_get_visitors_time_series without opening the 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?

The 'right now (or in the past n seconds)' phrasing implies the real-time use case, but there is no explicit when-to-use statement, no exclusions, and no naming of alternatives such as pirsch_get_visitors_time_series for historical data. Usage is inferable but not stated.

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