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

With annotations already declaring readOnly=false and destructive=false, the description adds real substance the annotations can't: the target URL is rewritten with UTM tags before redirect, defaults are shager/link/none, and values are slugified to lower-case-with-dashes. It does not mention what is returned (no output schema exists) nor when the idempotency_key matters, even though idempotentHint is false and the 24-hour retry window is a meaningful behavioral trait.

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 core action and the UTM side effect lead, with the disambiguation sentence after, which is the right order. Three sentences, no filler, though the defaults/slugification clause is compressed into a semicolon-joined fragment that reads more like a note than prose.

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 six-parameter mutation tool with no output schema, the description leaves two operationally important things unsaid: what a successful call returns (link id? short URL?) and how idempotency_key interacts with retries given idempotentHint=false. The UTM and defaults coverage is good, but an agent still cannot fully predict the result of calling it.

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 already 83%, so the schema carries most of the load. The description still earns credit by stating the concrete default values for source, medium and campaign together in one place and by documenting the normalization rule ("words become lower-case-with-dashes") that the schema never states. It adds nothing about workspace_id or idempotency_key, but those are well covered in the schema.

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?

Opens with a concrete verb+resource ("Makes a tracked short link for any web address") and immediately bounds the scope by listing the surfaces it serves (bio, story, email, ad). It also separates itself from the post-embedded link case via cta_url on create_post, so an agent can place it relative to at least one sibling 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 routing rule: use this for standalone links, but use cta_url on create_post for links inside posts because those are auto-tagged per account. It also points to list_links for the click data. What's missing is any guidance on the obvious near-sibling in the tool list, create_connect_link, which an agent could easily confuse with this one.

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