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

Annotations already declare a non-read-only, non-destructive, non-idempotent mutation, so the safety profile is covered. The description adds genuinely new behavioral context the annotations cannot convey: a 1-credit creation cost plus a 0.001-credit per-click cost, which is decision-relevant for an agent. It stops short of 5 by not covering code-collision behavior or auth requirements.

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?

Two short sentences, front-loaded with the action and followed by the cost model; every sentence contributes information an agent needs and there is no 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 creation tool with full schema coverage, no output schema, and annotations covering mutation semantics, the description supplies the key missing decision factor (cost). It is only slightly short by not indicating what the call returns (e.g., the short URL) or failure modes like a taken custom code.

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%, with both long_url and code fully documented including format constraints, so the schema carries parameter semantics. The description adds nothing about either parameter, making the baseline 3 correct.

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 ('Create a short link'), scoped to 'this project', which is unambiguous and clearly distinct from the sibling link_stats (read/analytics) tool. It doesn't explicitly name a sibling or contrast with one, keeping it just short of 5.

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 verb; there is no statement of when to create a link versus when to inspect existing links via link_stats, and no prerequisites or exclusions. Comparable to the calibration MID case where a bare 'update X settings' sentence earned a 2.

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