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

Annotations only declare destructiveHint/idempotentHint/readOnlyHint booleans; the description goes further and spells out the concrete consequences: new_tags REPLACES the entire existing tag list, and a new alias makes the old short URL stop working. That is exactly the impact detail an agent needs before a destructive update, plus the underlying PATCH /update semantics.

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?

Three short sentences, front-loaded with the WRITE label and the destructive warnings, followed by the alternative tool and endpoint. No filler, no repetition of the title.

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 7-parameter mutation tool with a fully documented schema, rich annotations and no output schema, the description covers operation type, minimum required input, destructive effects and the sibling boundary — nothing an agent needs to invoke it 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 the schema already documents each parameter's format and constraints (lengths, ISO 8601 pattern, null semantics). The description restates the field list and the new_* requirement but adds no per-parameter meaning beyond the schema, which is the baseline-3 case.

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 an explicit 'WRITE: change an existing short link' verb+resource and enumerates the mutable fields (alias, tags, expiry, description, click-analytics switch). It names the sibling that handles the one adjacent operation (tinyurl_change_destination), so an agent can separate it from the other tools without reading schemas.

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?

States the precondition 'At least one new_* field is required' and routes destination-URL changes to tinyurl_change_destination, which is a genuine when-not rule. It does not address the other adjacent siblings (e.g. tinyurl_set_link_archived, tinyurl_create_link), so it stops short of full alternatives coverage.

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