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

Annotations cover safety (readOnly, idempotent, no destruction), and the description goes well beyond them: it discloses the authentication/gating model (definitions free; borrowing chains and citations need an API key on a signed-in account, else arrays empty and `gated` reports withheld counts), the `pivotWhy` per-instrument field, and the fundamental semantic rule that meanings are separated on facts only.

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-loads the resource scope in the first sentence, then layers usage, semantic constraints, and gating. Dense and largely earned, though the middle paragraph is lengthy and could be tightened without losing substance.

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 return values need not be enumerated, yet the description still names key response fields (`pivotWhy`, `gated`) and explains what happens when the key is absent. For a one-parameter lookup tool, nothing an agent needs to invoke it correctly is missing.

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% for the single `term` parameter, so the baseline is already 3. The description adds meaning the schema lacks: exact case-insensitive matching behavior, and that an alias (a borrower's own label) still resolves to the family it borrows into.

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 precise scope: one defined term across the whole corpus, returning each distinct wording, its defining instruments, borrowing chains, cited defining provisions, and other-language labels. This is distinguishable from siblings like define_term or term_languages, and the concrete example ('producer' under WEEE vs Batteries Regulation vs PPWR) pins down what 'family' means.

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?

Gives an explicit trigger condition: ask this when a term is defined differently across instruments and the answer depends on which. It also clarifies the alias-query routing behavior. It does not, however, name sibling alternatives (e.g. define_term) to say when NOT to use this tool, so it stops short of a 5.

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