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

Annotations only declare readOnly=false, openWorld=true, idempotent=false, destructive=false. The description adds the traits that actually govern invocation: a once-per-hour rate limit, a cost ceiling (~1 credit or less), and an estimate-only dry-run mode. Those are exactly the facts an agent needs to avoid burning quota on a redundant scan.

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?

Three short sentences, front-loaded with the trigger condition, then constraints, then the exclusion. No filler and the most decision-relevant information comes first.

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 one-optional-param tool with no output schema, the definition covers trigger, cost, rate limit, and routing to the read tool. The only gap is what a scan returns or whether it is synchronous versus job-based, which would help an agent set expectations after the call.

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 sole `estimate` parameter is already described there ('true returns the credit cost without scanning'). The description restates that almost verbatim, adding only the workflow framing of cost-checking before spending credits, so it does not materially extend parameter meaning.

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 ('Rescans the accounts on their XcutAI watchlist') and names the sibling it must not be confused with (xcut_get_breakouts). An agent can pick it apart from get_breakouts without opening either 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?

Explicit trigger ('when the user wants fresh breakouts now instead of waiting for the next scheduled scan') plus an explicit exclusion and alternative ('Do not use to read the latest results (use xcut_get_breakouts)'). This is the when/when-not/alternative triad in full.

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