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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered; the description adds real value by stating the output is deterministic and computed offline. However, with no output schema, it never says what the returned ID actually looks like (format, length, prefix), which is the main behavioral unknown for a key-generating tool.

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 sentences, front-loaded with the derivation formula, then the determinism guarantee, then the intended use. No filler or repetition.

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?

For a simple, side-effect-free derivation tool with full schema coverage and rich annotations, the definition covers inputs, determinism and purpose. The only real omission is a description of the returned identifier, which matters because no output schema exists.

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% and each parameter already documents its format and example, so the schema carries the parameter burden. The description only restates the three inputs in prose and adds no normalization or edge-case semantics beyond the schema's own note that APN formatting is normalized.

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 names a specific output (a deterministic FactLot parcel ID) and the exact inputs that derive it (state FIPS, county FIPS, APN), which cleanly separates it from id_document, id_entity, id_space and id_parse. It stops short of explicitly naming those siblings, so an agent must infer the boundary from the resource word 'parcel'.

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?

'Use it as the join key across systems' implies the intended role but gives no when-to-use/when-not conditions and no routing against the other id_* tools. The usage context is inferable rather than stated.

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