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

The description does add real behavioral context beyond the annotations — the returned field (short_url) and the SMS shortcut — but it also asserts 'The same url again returns the same link,' which is idempotent behavior, while the annotations declare idempotentHint: false. Conversely, annotations flag destructiveHint: true and the description never mentions any destructive or irreversible effect, so an agent must reconcile two conflicting safety signals before retrying.

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?

Four short sentences, front-loaded with the core action and return value, then the dedup behavior, then the usage trigger. The closing sentence about shorten_links is slightly tangential but is a valuable routing hint rather than 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 two-parameter create tool with full schema coverage and no output schema, the description covers purpose, return field, repeat-call behavior, and the SMS alternative. It stops short of stating whether links are bound to a domain (relevant given create_link_domain) or what permissions are required.

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 100% and both parameters (url, name) carry their own descriptions, including the refusal of public shorteners and look-alike domains, so the schema does the heavy lifting. The prose adds no additional meaning about parameter format or constraints beyond what is already documented.

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 and resource — 'Make a tracked short link' — and immediately names the return value (short_url) and the contexts it is used in (text, ad, email). This is clearly distinguishable from siblings such as create_link_domain, list_links, and verify_link_domain 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?

Gives an explicit trigger ('Suggest this whenever someone wants to know whether a link gets clicked or leads to sales') and an explicit when-not-to-use route: for a link inside a text, set shorten_links: true on the send instead of calling this tool. That is a rare and genuinely useful routing instruction.

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