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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: the null-run case when nothing is active, plus the stall indicator, which an agent needs to interpret the response. It stops short of saying whether polling is expected or at what cadence, keeping it below 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?

One compact sentence front-loads the core action and its returned signals, followed by the null case and the sibling pointer. Every clause carries distinct information; nothing is redundant with the title or annotations.

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 no output schema, the description compensates by spelling out the returned fields (progress fraction, pace, ETA, stalled flag) and the empty-state semantics. For a one-parameter read tool, an agent has everything needed to call it and interpret the result.

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?

There is a single parameter (projectId) and schema description coverage is 100%, with the schema already telling the agent to source it from list_projects. The description adds no further meaning about the parameter, so the baseline of 3 for a well-documented schema 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 and resource ('Get the scan running for a site right now') and enumerates exactly what comes back: answers done of total, pace, time left, stalled status. It also distinguishes itself from siblings by noting that run is null when nothing is running and that finished scans live in list_scans.

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 an explicit triggering condition ('Use it after start_scan') and routes the agent elsewhere for the excluded case ('finished scans are in list_scans'). The alternative and the condition that selects it are both named, leaving little to infer.

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