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

Annotations already cover read-only, idempotent, and closed-world behavior, so the description correctly spends its space elsewhere: it discloses what the full view returns (passages, sources, trust fields, relationships, cite_as) and gives the content_hash recomputation rule, which is real verification context not derivable from annotations or schema. It omits failure behavior (unknown ID, version out of range) and whether trust/applicability are entitlements-gated.

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 sentences, front-loaded with the retrieval verb and the ID vocabulary before the optional modifiers. The content_hash sentence is dense and jargon-heavy but each clause carries information; no filler.

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?

An output schema exists, so the description doesn't need to restate return values, and it does enough: it identifies the addressable ID space, the two refinements (version, as_of), the view choice, and the hash-integrity check. The only meaningful hole is the compact-vs-full tradeoff, which matters for a tool whose default view is 'full'.

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?

It explains as_of as 'applicability on as_of' and clarifies the ID prefix vocabulary that the schema only expresses as an opaque regex, which adds genuine meaning. However, the view parameter's critical difference is left half-stated: it describes what 'full' contains but never says what 'compact' omits or why an agent would choose it.

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?

Opens with a specific verb+resource ('Fetches one object by ID') and enumerates the ID prefixes (prop_, auth_, case_, src_, rel_), which pins down exactly what entity types are addressable. It implicitly separates itself from search_evidence by emphasizing single-object retrieval, but never names a sibling, so it stops short of a 5.

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?

It signals that version and as_of are optional refinements ('optionally at a specific editorial version and for a date'), which hints at the point-in-time lookup use case. There is no explicit when-to-use/when-not guidance and no routing to search_evidence, build_evidence_packet, or get_relationships for related needs.

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