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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data. The description adds useful context that the source is a connected third-party calendar and that results default to upcoming events, but says nothing about result ordering, pagination, or what happens when no account is configured. With annotations carrying the safety burden, a 3 is appropriate.

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?

Three short sentences, front-loaded with the resource and scope, with no filler. Minor redundancy in repeating filtering capabilities that the schema already documents, but nothing that wastes the reader's attention.

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?

For a 7-parameter read tool with no output schema, the description covers the source and default behavior but omits what the response looks like (event fields, ordering, whether an empty result is reported) and how max_results/pagination behave. The account/channel disclosure noted in the schema is not surfaced in the description, which would help an agent interpret results.

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 every parameter including the date_from/date_to aliases and the account_id omission behavior is already documented in the schema. The description only restates the date-range and query filtering at a high level, adding no syntax or precedence detail beyond the schema. 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?

The description uses a specific verb+resource ("List events from the connected calendar") and even names the supported backends (Google, Outlook, CalDAV), so the agent knows exactly what is being read. It does not, however, contrast itself with the adjacent calendar tools such as calendar_check_availability, leaving the sibling distinction to be inferred from the names alone.

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?

"Shows upcoming events by default" plus "Can filter by date range and search query" implies when this tool is useful, but there is no explicit when-not guidance and no named alternative for cases like checking free/busy windows. Usage is implied rather than directed.

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