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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the write-but-non-destructive profile is covered. The description adds genuinely new behavior: it returns chatID, the message and an after cursor, and the message is editable/deletable within a 60-minute window. It omits rate limits or failure modes, so it stops short of a 5.

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?

A single dense sentence front-loads the action, then the targeting variants, then the negative guidance and return contract. No sentence is wasted, though the packed clauses around replies and returning cursors make it slightly heavy to parse in one pass.

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 7 parameters, 100% schema coverage and no output schema, the description supplies the missing return shape (chatID, message, after cursor) and the 60-minute edit window. Nothing an agent needs to select or invoke this tool correctly is absent.

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 description coverage is 100%, so every parameter including the idempotencyKey retry semantics is already documented in the schema. The description's notes that chatID equals a task ID and that userID is the DM alternative restate what the schema already says, rather than adding syntax or format meaning.

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+resource (sends a message on behalf of the token owner) and immediately distinguishes the three targeting modes: chatID, userID direct message, and replyMessageID. An agent can tell this apart from siblings like chat_read, chat_reaction, or chat_message_update without opening a schema.

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?

Gives explicit when-to-use ('blocking questions, replies to messages addressed to the token owner, and messages the user asks for') and explicit when-not ('not for status updates, summaries or links to created items'). This is precisely the routing guidance an agent needs among ~70 siblings.

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