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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds genuine domain context beyond annotations: the versioning model (valid_from, valid_until, superseded_by) and that each version carries provenance (source values), which an agent cannot get from the 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?

Three short, front-loaded sentences: purpose first, then the as_of behavior, then the shape of each version. Every sentence carries information and none is wasted.

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 takes on the job of describing the return shape, and it does so (versions with validity windows, superseded_by, and source values). Combined with annotations covering safety and 100% parameter coverage, it is nearly complete; only the pagination behavior of history_limit is left entirely to the 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 description coverage is 100%, so all three parameters are already documented in the schema, including as_of's date pattern and history_limit's default/range. The description's explanation of as_of duplicates the schema's temporal semantics without adding syntax or edge-case guidance, so the baseline 3 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?

The description states a specific verb and resource: it returns the current version plus history of a single fact, and explains the temporal scoping via as_of. It is clear what the tool does, but it never names or contrasts a sibling such as search_facts, so differentiation is left to inference.

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?

Usage is only implied: a single-fact lookup with an optional time-travel parameter, distinct from the sibling search_facts. There is no explicit statement of when to choose this tool over search_facts or the other get_* siblings, and no exclusions are given.

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