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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false, and openWorldHint=true. The description adds the instruction 'Only send fields explicitly requested,' which hints at partial-update behavior but does not disclose what happens to unspecified fields (e.g., whether they are left unchanged or reset). It also does not mention whether the operation is reversible or what side effects occur. The description does not contradict the annotations, but it adds only modest behavioral context beyond them.

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 description is a single sentence that front-loads the core purpose and ends with a practical usage rule. It is concise and every clause earns its place. It could be slightly improved by naming an alternative tool, but as written it is efficient and clear.

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?

The tool has 8 parameters, no output schema, and only 38% schema description coverage, so the description carries a heavy burden. It covers the main state categories and the partial-update rule, but it does not explain the 'name' parameter, the muted_until union type, or the behavior of unspecified fields. For a mutation tool with no output schema, an agent would likely need more detail to call it correctly in edge cases, though the chat_id guidance in the schema helps.

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 only 38%, so the description must compensate. The description names the state dimensions (read/unread, archive/pin, label, mute metadata) which maps to several parameters (read_status, archive_status, pin_status, label, muted_until). It also adds the key guidance 'Only send fields explicitly requested,' which clarifies that parameters are optional and partial updates are intended. However, it does not explain the meaning of 'name' or the boolean/string union for muted_until, so it does not fully compensate for the low coverage.

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 a clear verb ('Update') and resource ('supported chat state') and enumerates the state dimensions (read/unread, archive/pin, label, mute metadata). It is distinguishable from siblings like messaging_set_composing and messaging_set_presence, though it does not explicitly name them. The title 'Messaging: Set chat state' reinforces the purpose, so the description adds enough specificity to avoid confusion.

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?

The description gives a partial usage rule: 'Only send fields explicitly requested.' This implies the tool is for updating only the fields the user asked for, which is useful guidance. However, it does not explicitly state when to use this tool versus alternatives like messaging_set_composing, messaging_set_presence, or email_mark_read, nor does it mention prerequisites like needing a valid chat_id. The guidance is implied rather than explicit, so it earns a 3.

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