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

Beyond the readOnlyHint annotation, the description discloses the credit cost ('1 credit'), account requirement, and the behavior of returning a signup link if no account exists. It also specifies what data is fetched per platform, adding value beyond the annotation. However, it omits error specifics or rate limits.

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 two terse sentences, front-loaded with the primary action and immediately followed by relevant details (platform fields, credit, read-only, account note). Every word serves a purpose, with no redundancy or filler.

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 simple 2-parameter read-only tool without an output schema, the description thoroughly explains the return value per platform, cost, and account prerequisite. It lacks an explicit return format or error-handling details, but for typical use it is sufficiently complete.

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?

The schema already covers both parameters with descriptions, but the tool description adds meaning by explaining that the 'platform' parameter determines which fields are returned (reddit: account age, karma; hackernews: about, created). This deepens understanding of how parameters affect the output beyond the schema's basic enum values.

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 opens with 'Fetch a user profile', a specific verb-object pair that clearly identifies the tool's function. It further differentiates from siblings by listing platform-specific data (reddit vs hackernews fields), which distinguishes it from social_get_post and social_get_user_activity.

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 provides context on when to use the tool (fetching user profiles) and adds practical notes like '1 credit' and account requirement, but it does not explicitly contrast with alternative tools or state exclusions. Usage is implied rather than explicitly guided.

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