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

Annotations already declare readOnlyHint, openWorldHint and destructiveHint=false, so safety is covered. The description goes beyond them by disclosing the returned field set (name, color, overlap rule, active state, links), which partially substitutes for the absent output schema; it omits error/auth behavior.

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?

Two tight sentences with the identity and returned fields front-loaded, followed by the endpoint. No filler and nothing redundant.

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 single-parameter read tool with annotations covering safety, the description covers identity and return fields, compensating for the missing output schema. Minor gaps remain around failure modes (e.g., unknown id) and auth, so it stops short of fully complete.

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% for the single required subcalendar_id, so the schema already documents it fully. The description adds no syntax, format, or constraint detail beyond 'by id', so the 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 and resource ('Get sub-calendar') plus the scope ('by id'), and the phrase 'One sub-calendar' implicitly distinguishes it from the list_subcalendars sibling. It even enumerates the fields returned, so an agent knows exactly what this call yields.

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?

The 'by id' scope implies this is the single-item lookup versus the list variant, but there is no explicit when-to-use, no named alternative, and no stated prerequisites. Usage is inferable but not spelled out.

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