Reply to a comment

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

Annotations already declare a non-read-only, non-idempotent, open-world write, so the safety profile is covered. The description adds two genuinely useful facts beyond them: the reply is publicly visible and writes must be enabled via IG_ENABLE_WRITES. It says nothing about rate limits, moderation, or failure behavior.

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?

Two short sentences, action first, prerequisite second, with no filler. Every clause carries information an agent needs.

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 two-parameter mutation with annotations and no output schema, the description covers the key facts (public write, writes flag) but leaves the undocumented comment_id parameter and post-call behavior unexplained. Adequate but with clear 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 description coverage is only 50% – comment_id has no description and only a numeric pattern – and the description compensates with nothing about either parameter. It neither explains the ID format/ownership nor clarifies message constraints beyond what the schema already states.

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 (posts) and resource (a public reply to a comment), which is clearly distinct from ig_comment_on_media's top-level commenting action. It does not, however, explicitly contrast itself with the closest siblings such as ig_comment_on_media or ig_list_replies.

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 supplies a real precondition ('Requires IG_ENABLE_WRITES=true'), which tells the agent when the call will be permitted. It gives no guidance on choosing this tool over alternatives like ig_comment_on_media, so usage is only implied by the name and the gating flag.

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