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

Annotations already declare readOnly/openWorld/non-destructive, so the safety profile is covered. The description adds genuinely new behavior: that `time_zone` is what resolves "today" and that `since` returns only changes after an earlier server_time, which is non-obvious delta semantics. It doesn't discuss pagination or read-budget truncation beyond the schema's include_all_dates note.

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-loaded with the verb+resource, then usage, then parameter semantics—a sensible order with no filler sentences. The first sentence is a long enumerative run-on, but each listed item carries information in the absence of an output schema.

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 correctly takes on the burden of describing return contents and does so thoroughly, plus it explains the delta and time-zone behaviors. Minor gap: it doesn't note result-size/truncation behavior, which is left to the include_all_dates schema text.

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 baseline is 3. The description earns above baseline by explaining the functional role of two parameters—`time_zone` as the anchor for today's date and `since` as a delta cursor against a prior server_time—which the schema text alone only hints at.

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 ("Reads a saved plan") and then enumerates the payload (title, event details, participants, availability, RSVP, best dates, places with votes, currency), so an agent knows exactly what comes back. It does not explicitly differentiate itself from siblings like find_plan_mentions or open_planner, which keeps it below a 5.

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?

"Use when the user shares a plan link or asks about a plan's current state" gives a concrete trigger condition. It also implies the incremental-refresh case via the `since` sentence. No explicit when-not conditions or named alternatives are provided.

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