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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds genuinely non-obvious behavior on the error path: a miss returns 'not_found' with nearest real units either side plus `same_segment` hints for paths ending in the asked-for segment. The gap is that it never says what metadata fields come back, which matters since there is no output schema.

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 purpose, then the URN construction rule, then the error semantics — a sensible order. The second paragraph is dense but every clause carries information; nothing reads as 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?

With no output schema and no annotations about return shape, the description should say what 'metadata' comprises (title, type, dates, in-force status?). That omission is the main incompleteness. Everything needed to construct a valid call and interpret a miss is covered.

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% and the schema already says the URN comes from get_document_toc, so the baseline is 3. The description does add the template `urn:ua:law:{nreg}:{path}@{YYYYMMDD}` and the truncation rules, which is real meaning beyond the schema, but it stays at the level of how to construct rather than what each segment means.

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 resource and scope: 'Metadata for one structural unit, addressed by its URN.' The word 'Metadata' distinguishes it in spirit from the sibling get_unit_fulltext / get_unit_editions / get_unit_in_force, but the description never names those siblings, so the differentiation is implicit rather than stated.

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?

Explicitly routes the agent to a filtered `get_document_toc` to source the URN 'rather than building it,' which is clear when-to-use guidance. It also explains the two URN truncation variants (drop the date for today's edition, drop the path for the whole document). It stops short of saying when to prefer get_unit_fulltext or get_unit_editions instead.

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