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

Annotations already carry readOnly/idempotent/non-destructive/openWorld, so the description's real value is the behavioral detail it adds: output is validated against Google's rich result rules and unreadable values are marked TODO rather than fabricated. That is useful non-obvious behavior for an agent to know, though nothing is said about how validation failures are surfaced.

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?

Front-loaded with the core action and constraint, then the type list. The enumeration is long but each entry carries a derivation hint, so little is wasted; a slightly tighter phrasing would earn 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?

There is no output schema, so the description must characterize the return, and it does: a JSON-LD block plus validation against rich result rules, with TODO markers for missing values. It stops short of describing the validation result shape, leaving a minor gap for a tool with no output schema.

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%, so the schema floor is 3, but the description adds real meaning beyond the enum labels: it explains how FAQPage is built from question headings, how Organization pulls sameAs links, how BreadcrumbList derives from the URL, and that 'auto' selects the best fit. That meaningfully enriches the parameter choice.

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 ('Generate a JSON-LD block for a page from its own content') and adds a distinct validating behavior. It clearly separates itself from the validate_schema sibling by being the generator whose output is checked against Google's rich result rules.

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 enumerates the supported types and their derivation sources, which implies when each is appropriate, and explains 'auto' as picking the best fit. However it never says when to choose this tool over the closely related validate_schema sibling, so routing guidance is only implied.

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