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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is covered; the description adds the substantive part: only pending messages are affected, destination and sender are immutable, omitted fields are preserved, and timezone falls back to the message's saved value. It does not say what happens when the frozen destination/sender is passed or what a stale revision produces, which is the main residual gap for a destructive mutation.

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 the mutation scope, then prerequisites, then immutability, then partial-update semantics. Nothing is filler; the only mild duplication is the approval sentence overlapping the confirmed parameter description.

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 7-parameter destructive mutation with annotations but no output schema, the description covers the non-obvious behavior an agent needs: partial update, timezone inheritance, revision freshness, and fixed destination/sender. Conflict/error handling for a stale revision is the one omission that would matter in practice.

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 86%, so the baseline is 3 and the schema already explains at, text, timezone, revision, confirmed and request_id well. The description adds genuine PATCH semantics ("Omitted text or time stays unchanged") and the timezone inheritance default, but nothing beyond the schema for revision conflict behavior or the id format.

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?

"Change time and/or exact text of a pending scheduled message" gives a specific verb plus resource and bounds the editable surface, which separates it in practice from telegram_edit_message (already-sent messages) and telegram_schedule_message (creates). It does not name a sibling explicitly, so an agent must infer the boundary from the word "pending".

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 states prerequisites ("Read the current revision first") and approval requirements ("Obtain approval for the revised text and local date/time"), which tells the agent how to sequence the call rather than just what it does. It stops short of naming explicit alternatives such as cancel_scheduled_message for removal or list_scheduled_messages as the source of the revision.

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