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

Annotations already declare readOnlyHint, idempotentHint and closed-world, so safety is covered. The description adds genuinely new context in a payment-oriented toolset: it is free and requires no payment, stated twice. It also discloses the stateful return behavior (progress vs. findings, re-scan comparison), which annotations do not convey.

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?

The return-content enumeration is well front-loaded and informative, but the payment claim is stated twice ('Free.' at the opening and again as 'This tool is free; no payment is required.'), which is pure redundancy. Removing the duplicate would leave a tight, high-value sentence.

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?

An output schema exists, so return values need not be spelled out, yet the description usefully summarises the shape of results across the scanning and completed phases. Combined with complete schema coverage and annotations, an agent has enough to call this correctly; only the explicit relationship to sibling reach/reach_report_rescan 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 description coverage is 100% and the single report_id parameter is fully documented there, so the schema carries the load. The description only restates that the report is addressed 'by its report_id' and adds no format, provenance or validation detail beyond the schema.

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 ('Returns a reachability report by its report_id') and enumerates the two response states an agent will encounter: in-progress while scanning, then prioritised findings with causes, fix steps and reproducing commands. This also implicitly distinguishes it from sibling reach_report_rescan, which starts a new scan rather than reading one.

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 mention of 'progress while it scans' implies this is the tool to poll after ordering a report, and 'a comparison with the previous scan after a re-scan' hints at follow-up after reach_report_rescan. However, no alternative is named and no explicit when/when-not condition is given; the agent must infer the polling workflow.

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