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 bar is lower; the description still adds real behavior: every value carries a source page and read date, is signed by the listing market's node and receipted, and absent fields return not_on_record rather than being omitted. It also enumerates the typed error taxonomy (unknown_issuer, ambiguous, not_on_record, invalid_request), which is genuinely useful for failure handling.

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 purpose is front-loaded in the first clause, which is good, but the single run-on sentence is dense with unexplained jargon ('receipted', 'Door:', 'signed by the node') and could be split into purpose, returns, and errors. Size is reasonable; readability suffers.

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, the description correctly carries the return-value burden: it lists the returned fields, provenance metadata, and the not_on_record convention, plus the error set. The main gap for a 3-parameter lookup is the lack of any statement about how it differs from resolve_issuer.

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, and the description largely restates the schema's identifiers (ticker, ISIN, LEI, exchange). It adds one real clarification — 'a ticker and its exchange' implies exchange should accompany a ticker identifier — but does not explain how market relates to exchange or when market alone is sufficient.

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 opening clause names the resource and the lookup direction ('the issuer behind a ticker') and enumerates the returned fields (issuer, ISIN, LEI, listing, status), so an agent can tell what it gets back. It never distinguishes itself from the sibling resolve_issuer, which sounds like an overlapping lookup, so differentiation is left to inference.

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?

There is no explicit when-to-use statement and no comparison against resolve_issuer or list_nodes, despite resolve_issuer being an obvious candidate for the same lookup intent. The only routing hint is 'every node door answers it for its own market', which explains deployment rather than tool selection.

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