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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false, but the description adds substantial behavioral context: it accepts either a LEI or a company name (resolved automatically and echoed back), returns a full set (bonds, share lines, ADRs) rather than a single value, and explicitly handles the empty-set case for existing entities. No annotation contradiction.

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?

The description is three sentences, front-loaded with the primary action, and every sentence earns its place. It efficiently covers input flexibility, output semantics, and an edge case without redundancy or fluff.

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?

There is no output schema, so the description carries the burden of explaining return values. It does this explicitly by stating the full-set return (bonds, share lines, ADRs) and the empty-set behavior. It also mentions the official GLEIF source, providing complete context for a single-parameter tool.

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%, so the baseline is 3. The description adds meaningful semantics beyond the schema by clarifying that the single parameter accepts both a 20-character LEI and a company name, and that names are resolved via the LEI registry and echoed back. This extra detail justifies a score above baseline.

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 clearly states the action: 'List ALL ISINs (securities) issued by a legal entity'. It uses a specific verb and resource, and identifies the scope. This distinguishes it from sibling tools like isin_to_lei (reverse direction) and get_lei (entity details), making the purpose unambiguous.

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?

The description provides clear use cases with example queries ('what securities has this company issued' / 'all ISINs for Nestlé') and mentions the source mapping, implicitly positioning this as the forward ISIN lookup tool. It doesn't explicitly state when not to use it or name alternatives, but the context is strong enough for an agent to select it appropriately.

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