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

Annotations already cover safety (readOnly, idempotent, non-destructive), and the description adds substantial extra context: a plan gating requirement, newest-first ordering, a 20-per-page limit, and the history_truncated caveat for very large histories. These are exactly the behavioral traits an agent needs and none are derivable from the structured fields.

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 gating constraint ('Requires a Pro plan'), then the return shape and pagination, with no filler sentences. It is dense but every clause earns its place; the long enumerated field list is justified because no output schema exists.

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: it lists returned fields (event, year, dates, city, country, tier, booths, as_of), explains ordering, page size, cursor pagination, and the truncation flag. An agent has everything needed to call and interpret this 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 description coverage is 100%, so role, cursor, company, to_year and from_year are already fully documented in the schema. The description echoes the role/year filtering and cursor usage but adds no syntax, format, or edge-case detail beyond what the schema provides, 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+resource: 'Every edition one company exhibited at or sponsored.' An agent can immediately distinguish this per-company cross-edition history from the per-edition sibling list_edition_exhibitors, and the field list clarifies what it returns.

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 a clear prerequisite ('Requires a Pro plan') and the pagination flow ('pass cursor from the previous answer for the next page'), plus filter options by role and year range. It does not explicitly name an alternative sibling or state when-not to use it, so it falls 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.