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

Annotations already mark this read-only, idempotent and non-destructive, but the description goes well beyond them: 403 gating on plan tier, `key_lacks_analytics`, `pending` delivery lag of 24-48h, the full set of non-ready status values with their fixes, `reported: false`/null semantics, and the warning not to read an empty series as zero. That is exactly the behavioral context an agent cannot get from the schema.

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?

Dense but front-loaded: the funnel definition comes first, then data sources, then prerequisites, then the status/error protocol. Every clause carries information, though the status enumeration is long enough that it reads as a wall of text rather than a tight structure.

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 exists, yet the description explains what comes back (funnel metrics, conversion rates, source breakdown, daily series, status/message, reported flags) and how to interpret gaps. For a complex, connection-gated analytics tool, the agent has everything needed to call it and to avoid misreading results.

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 all five parameters (including the `store` enum and window semantics) are already documented in the schema. The description reinforces the ASC-definition subtlety (impressions include product page views) and the Sales-report provenance of downloads, but adds little per-parameter meaning beyond that, 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+resource (App Store Connect App Analytics funnel for one of your own iOS apps) and enumerates exactly what it returns: impressions → page views → downloads, conversion rates, search share, sources, installs, deletions, sessions. The iOS-only framing plus 'Downloads come from the Sales report' distinguishes it from siblings like sonar_app_sales and sonar_app_revenue.

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 clear context for use: requires Agency plan and an ASC connection with an Admin-role key, and tells the agent to always check `status` before reading data. It does not, however, name a sibling alternative or state explicitly when to prefer sonar_app_sales / sonar_app_overview instead, so it falls short of a 5.

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