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

Beyond the annotations (which already declare read-only, idempotent, closed-world, non-destructive), the description discloses substantial behavior: signed records with node signature (kid) and RCO-10060 receipt, source and read date on every field, the Replay store under Data Vintage covering sealed market-years from 2021 forward. It also enumerates the typed error outcomes and the precise fallback semantics (before_record, not_sealed naming the earliest sealed date), which no annotation or schema field conveys.

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, and the remainder is information-dense rather than padded. The second half is a long run-on that packs vintage scope, error taxonomy, and receipt verification together, making it slightly harder to scan than it could be.

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 carries the full burden of describing the return value and does so: the signed record, per-field source and read date, sealed disclosure lines, error variants, and receipt verification path. An agent has enough to call it and interpret both success and failure answers.

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%, so the schema already documents as_of, issuer formats, and the optional market code. The description restates ticker/ISIN/LEI and the date but adds little syntactic meaning beyond the schema, so the baseline of 3 applies.

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 states a specific verb and resource: it returns the issuer record as it stood on a given date, keyed by ticker, ISIN or LEI plus a date. It does not explicitly name the sibling that handles identifier resolution (resolve_issuer) or list_events_since, so the differentiation from alternatives is left 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?

Usage context is implied rather than specified: 'so a backtest can show what it read and when' signals the historical/audit use case. There is no explicit when-not guidance or routing to resolve_issuer for unknown identifiers, leaving the agent to infer the boundary conditions from the typed-error list.

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