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

Annotations only say it is a non-read-only, non-destructive, non-idempotent mutation; the description adds genuinely non-obvious behavior: per-call cost of $0.001 with no charge on failure, that changing the target makes future runs execute as this bot, and that resuming skips missed slots rather than backfilling. That is exactly the kind of context annotations cannot carry.

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?

Five short sentences, front-loaded with what changes and what to pass, then consequences (bot identity, resume behavior), then cost. No sentence is a restatement of the name or the 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?

For a mutation with a nested-object param, annotations, and no output schema, the description covers scope, partial-update contract, and side effects. It leaves unstated what a successful call returns (e.g., the updated schedule) and what happens when timetable and time_zone are changed together, which are the remaining gaps.

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 67% and the timetable nested object is already well documented in-schema, so the description's job is to add the patch contract, which it does ("Give only what changes", "Changing what it runs" for arguments). It adds little on schedule_id or the timetable shapes beyond what the schema states, so it is additive but not comprehensive.

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?

Specific verb+resource ("Change a schedule") followed by an enumeration of exactly which fields can be changed (name, arguments, timetable, time zone, paused). An agent can distinguish it from schedules_create/schedules_delete/schedules_get by the verb alone. It stops short of naming siblings explicitly, which keeps it from the top band.

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?

"Give only what changes" states partial-update semantics, and "or pause and resume it" documents how to reach the paused lifecycle without a separate tool. What's missing is explicit routing guidance against siblings (e.g., when to use schedules_run_later instead of editing a timetable), so no exclusions are stated.

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