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

Annotations already cover read-only/idempotent/non-destructive, but the description goes much further: it enumerates the four return states, explains that `uncertain` means an open bracket around a rename/ISIN change, and warns that `out_of_coverage` must not be reported as 'no such symbol'. That is exactly the behavioral context an agent needs.

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?

Dense but front-loaded: what it does, when to use it, what it returns, and how to read each state. No filler sentences, though it is on the longer side and could tighten the back half slightly.

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 return-value burden and does so fully, including the meaning of each status and the coverage-window caveat. Nothing essential for correct invocation 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 description coverage is 100%, so the schema already documents date, kind, and value. The description reinforces the symbol/ISIN distinction and date anchoring but adds little syntax or format detail beyond the schema, so baseline 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?

States a specific verb (resolve), a specific resource (historical symbol or ISIN), and the temporal scope ('ON a given date'). This is clearly distinguishable from sibling tools like get_identifiers_asof, which presumably go the other direction.

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 explicit when-to-use context with concrete scenarios (2018 holdings file, old research note, backtest) and a clear failure mode to avoid (merging two companies after ticker recycling). It doesn't name a sibling alternative for current-data lookups, so it stops short of a full 5.

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