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

The annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-obvious operational context: a $0.05 cost, an API key requirement, and a 92-day cap on the range. It stops short of stating what an out-of-range or empty result looks like.

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?

The scoping rules come first and the row shape second, with no filler sentences. The telegraphic fragment style is dense but readable, and every clause (default, cap, ordering, fields, price, auth) carries information.

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 three-parameter read tool with an output schema, the description covers scoping, default, range limit, ordering, cost, and auth. Return values are listed even though an output schema exists, so the only real gap is behavior on empty or invalid input.

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 100%, so the three parameters are already documented in the schema, which sets the baseline at 3. The description does add value the schema lacks — 'Default today' and the 92-day maximum — but it does not clarify precedence or interaction when both 'date' and 'from'/'to' are supplied.

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 states the resource ('The user's time blocks by day') and the ordering ('earliest first'), which is enough for an agent to recognize this as the read-side counterpart to add_time_block and update_time_block. The retrieval verb is only implied by the tool name rather than stated in the description, so it is clear but not perfectly self-contained.

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?

It tells the agent exactly how to scope the query: either 'date' or 'from/to', with an explicit 92-day ceiling and 'Default today' when nothing is supplied. That resolves the main selection ambiguity (single day vs range), though it never names a sibling tool or an exclusion case.

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