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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true. The description adds substantial behavior beyond this: it states the observation is deterministic, records only a bounded representation, refuses private/internal addresses, bounds redirects/response size/timeouts, and discloses the arithmetic nature of comparison. It also clarifies cost and lack of payment capability. No contradiction with annotations.

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 description is reasonably concise but dense with information. It is front-loaded with 'DETERMINISTIC OBSERVATION', and every sentence conveys meaningful content about behavior, constraints, or uncertainty. A slight vocabulary/format overhead prevents a 5.

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?

Given there is no output schema, the description fully explains the return values (BASELINE_CREATED, NO_CHANGE, CONTENT_CHANGED) and their arithmetic basis. It also covers restrictions, uncertainty, and cost. For a tool with one parameter and clear behavior, this description is complete and self-contained.

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% (url is described as 'Absolute http(s) URL of a lawful, public, non-credentialed page'). The description adds meaning by explicitly stating that private, loopback, and internal addresses are refused, and by describing how the URL is used (fetched, recorded). This goes beyond the schema's baseline of 3, though it doesn't introduce wholly new parameter semantics.

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?

The description uses a specific verb ('fetches', 'records') and names the resource ('one lawful public web page'). It clearly distinguishes from the sibling tool by stating 'Makes no claim about meaning', positioning it as purely observational rather than interpretive.

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 description gives clear context on when to use this tool (for deterministic observation of public pages) and what to expect (arithmetic comparison, not semantic meaning). It does not explicitly name the alternative tool 'interpret_commercial_change' for semantic interpretation, but the contrast is strongly implied. Limitations like private/loopback refusal and rate limiting are provided.

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