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

Annotations already declare non-idempotency and write semantics, but the description adds the mechanism behind idempotentHint=false (a second alias-less call creates a duplicate link) and notes the return value ('the new tiny_url') plus the HTTP surface (POST /create). It does not mention auth/rate-limit behavior or what happens on alias collision.

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 compact sentences, front-loaded with the operation type and the single required target, followed by optional fields and the critical non-idempotency caveat. 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?

With no output schema, the description correctly compensates by naming the returned field (tiny_url); with full schema coverage and annotations covering safety, nothing an agent needs to invoke this correctly is missing.

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 all six parameters are already documented in the schema, and the description's field summary (alias, domain, tags, expiry, description) largely echoes it. Baseline 3 applies since the schema carries the parameter detail.

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 ONE new short link for an http(s) destination URL') and the WRITE prefix signals mutation immediately, distinguishing it from read siblings like tinyurl_get_link. An agent can tell it creates a brand-new link rather than modifying one, which separates it from tinyurl_update_link and tinyurl_change_destination.

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?

It gives an explicit behavioral rule for repeated invocation ('not idempotent: calling it again without an alias creates another link'), which is genuine usage guidance. However, it never names the alternative tools for modifying an existing link, so the when-not-to-use-this routing is implicit.

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