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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial context beyond them: a fixed 28-complete-UTC-day window, up to 12-hour caching, hostname-exact scoping, independent (non-funnel) event counts, and the caveat that missing/failed states are not zero traffic. This is exactly the behavioral context an agent needs before trusting the numbers.

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?

Four sentences, front-loaded with the core action, then windowing/caching, then interpretation caveats, then a security note. Every sentence carries distinct, non-redundant information; nothing is padding.

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 annotations covering safety and an output schema handling return structure, the description supplies the remaining essentials: freshness/staleness, scope, and semantic pitfalls in reading the data, plus a prompt-injection warning. Nothing an agent needs to invoke or interpret this tool is missing.

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 siteId parameter is already documented as 'Owned Nimo site ID.' The description adds minor meaning by clarifying scope is 'the site's exact hostname,' but cannot go much beyond the schema for a one-param tool, so baseline 3 is appropriate.

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: 'Read bounded aggregate site analytics through the PostHog connection.' It is clearly distinguishable from the connection-management siblings (connect_posthog, get_posthog_connection_status) by centering on reading analytics data rather than managing the connection.

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 phrase 'through the PostHog connection already stored securely by Nimo' implies a prerequisite (a connection must exist) but stops short of naming an alternative tool or stating explicitly when to use this versus get_posthog_connection_status or get_site. Usage is implied rather than directed.

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