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

With no annotations present, the description carries the full disclosure burden, and it does add real operational context: a fixed cost of 3 credits and a Bearer api_key auth requirement. It stops short of describing failure modes (private/nonexistent accounts) or rate limits, but the cost and auth disclosure is genuinely useful.

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?

Front-loaded with the purpose and returned fields, followed by short operational facts. Slightly marred by a doubled period after 'media' and by template-style fragments ('Platform=snapchat resource=user'), but nothing is verbose.

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?

There is no output schema, and the description compensates by enumerating the returned profile fields, plus it covers auth and credit cost for a simple one-parameter fetch. Enough for an agent to invoke correctly, though error/edge behavior is left unstated.

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% and the single 'name' parameter is already documented as a Snapchat username without '@'. The description's 'by username' adds nothing beyond the schema, so the baseline 3 applies.

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?

Specific verb (Fetch) + resource (public Snapchat profile) + scope (by username) + the fields returned (bio, subscribers, profile media). Naming the platform disambiguates it from the near-identical siblings instagram_user, tiktok_user, and threads_user, so an agent can pick it 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?

Usage is only implied by the purpose: fetch a Snapchat profile when you have a username. There is no explicit when-to-use, no statement of when this is the wrong choice, and no routing to an alternative such as a generic lookup tool or the platform-specific user endpoints.

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