Verify a Telegram recipient

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

No annotations are provided, so the description carries the full burden. It discloses the return values ('returns display name + photo') and clarifies the optional 'months' parameter for premium. It does not mention side effects or error scenarios, but for a simple lookup tool, the key behavioral traits are conveyed adequately.

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 extremely concise: two sentences that front-load the primary purpose and then add relevant details. Every word earns its place, 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?

The tool is simple with 3 parameters and no output schema. The description covers the purpose, the context of use, and what it returns. It omits error cases or edge behaviors, but these are likely non-critical for a lookup tool, making the description sufficiently complete for the tool's complexity.

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%, so the baseline is 3. The description adds minimal value beyond the schema, such as 'For premium, pass months' which aligns with the existing enum. It does not add new semantic depth for username or product, but it is not misleading.

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 clearly states the verb 'Look up' and the resource 'a Telegram @username', with a specific purpose ('before buying, to confirm the right person'). It also differentiates from sibling buy tools by noting 'buy tools also resolve usernames themselves', making it distinct.

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 clear usage context: 'before buying' to verify the recipient. It also notes that this is optional because 'buy tools also resolve usernames themselves', which implies alternatives. However, it does not explicitly state when not to use or provide direct comparison with sibling tools, but the guidance is sufficient.

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