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

Annotations already cover read-only and open-world. The description adds genuinely non-obvious behavior: accounts that opted out of search indexing are refused, the data is read from the account's own server, and the call costs 1 credit. That is real context beyond the structured fields.

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?

Three short sentences, front-loaded with what is returned and followed by constraints. The standalone 'Profile.' opener is dead weight but the remainder earns its place.

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?

No output schema exists, and the description compensates by listing the returned fields, plus refusal and cost behavior. Only the undocumented cache_max_age parameter is left unexplained.

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 50%: handle is well documented in the schema, but cache_max_age has no description anywhere. The description makes no attempt to explain caching semantics or acceptable values, so it fails to compensate for the gap.

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?

Names the resource (a public Mastodon account) and enumerates exactly what is retrieved: follower/following/post counts, bio, avatar, header, profile links. Distinguishes itself from mastodon_post and mastodon_userPosts through that field list, though the leading fragment 'Profile.' adds nothing.

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?

Implied usage ('a public Mastodon account, read from its own server') gives an agent enough to infer this is the identity/lookup tool versus the post-oriented siblings, but there is no explicit when-to-use or when-not guidance and no sibling is named.

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