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

Annotations already declare destructiveHint=true and openWorldHint=true, so the description's added value is what counts: it discloses merge semantics (only passed fields change), a billing exception (disabling works on a lapsed plan), and a recipient dedupe rule after edits. What it does not disclose is what 'destructive' actually means here — e.g. whether passing keywords replaces the whole list — nor any permission requirements.

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?

Four short sentences, front-loaded with purpose, then merge semantics, then the plan exception, then the dedupe caveat. No restatement of the title or of schema content, and every sentence carries a distinct operational fact.

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 destructive, no-output-schema mutation this covers the essentials: partial-update behavior, an availability exception, and post-edit recipient behavior. Gaps remain around permissions, what a failed update returns, and how array fields like keywords behave on replacement, but nothing an agent needs to select the tool is missing.

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% and the per-parameter text is already rich (disclosure_missing, whole-word keyword matching, post_id/null scope), so the schema does the heavy lifting and the baseline of 3 applies. The one genuine addition is the partial-update guarantee ('Only the fields you pass change'), which the schema does not state about omitted fields.

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 ('Changes an Instagram comment DM rule') and immediately clarifies the toggle case via 'enabled'. The verb alone separates it from create_comment_dm_rule and delete_comment_dm_rule in the sibling list, so an agent can route 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?

'turns it on or off with enabled' and 'Only the fields you pass change' tell the agent this is the mutation path for existing rules, including the pause/resume shortcut. It gives clear context but never explicitly says when to use create_comment_dm_rule or delete_comment_dm_rule instead, so exclusions are left implicit.

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