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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely new context the annotations cannot express: this is a paid call costing $0.05, and it returns a response-sample hash and timestamp. It omits any mention of rate limits, failure/error behavior, or what happens when the URL is unreachable.

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?

Two tight sentences: the first front-loads the paid, read-only preflight purpose and its outputs, the second delivers the exclusion boundary. No filler, no restatement of the tool name, and the cost is placed where an agent will see it immediately.

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 single-parameter tool with no output schema, the description supplies cost, what is checked, and a partial picture of the return payload (hash, timestamp). An agent still lacks detail on error outcomes and the exact response shape, but the core decision inputs are present.

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 and schema description coverage is 100% ('Public http/https evidence URL including scheme'), so the schema already carries the full burden. The description adds no format, constraint, or example detail beyond the schema, making the baseline of 3 correct.

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?

Names a specific verb and resource ('URL evidence preflight') and enumerates what it checks (HTTP accessibility, operational risk flags) plus what it returns (response-sample hash, timestamp). The explicit 'does not fact-check...' boundary sharpens the purpose further. It stops short of 5 because it never distinguishes itself from the sibling gridwatch_preflight, which an agent could easily confuse with this preflight tool.

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 a strong negative scoping clause: it does not fact-check claims, establish source credibility, or verify factual truth, which tells the agent when this tool is the wrong choice. It does not, however, name an alternative tool to use instead, nor state prerequisites beyond the URL being public http/https.

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