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

Annotations already declare readOnly, idempotent, closed-world, non-destructive, so the safety profile is covered. The description adds two pieces of context the annotations cannot: the required auth scope and the warning that user-written text arrives in untrusted_fields and must be shown, not obeyed.

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 with the core action front-loaded and no filler. The untrusted_fields sentence is slightly dense and assumes the reader knows that field name, but it carries real signal.

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 simple read-only single-record tool with full annotation coverage and no output schema, the definition covers auth and output-trust handling. It still omits what the block payload contains and what happens when the id does not exist, which matters for correct invocation.

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 coverage is 0% and the single `id` parameter is never explained. The description does not say whether the id identifies a calendar block, a busy block, or an event, nor what format it takes, so the agent is left to infer the key semantics of the only input.

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?

"Get a calendar block" names a verb and a resource, but the sentence essentially restates the title and adds nothing about what a 'block' is (busy block vs. calendar entry) or how it differs from siblings like list_calendar_blocks, get_calendar_days, or get_calendar_feed.

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 required `calendar:read` scope is a useful prerequisite, and the singular-object/`id` shape implies this is the single-record counterpart to list_calendar_blocks. However, no explicit when-to-use or when-not-to-use guidance or sibling routing is given.

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