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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=false, so the safety profile is covered structurally. The description adds nothing beyond that: it doesn't say whether adding is additive vs. replacing, whether the wordlist must be non-empty, whether duplicates are silently ignored (the schema says so, the description does not), or what a partial failure looks like.

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, nothing padded. But the second sentence is near-duplicative of the first, so it only barely earns its place — the sole new information is the word 'existing'.

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 mutation tool with no output schema, the description should disclose at least the duplicate-handling behavior (it is only in the schema), whether the call is additive to existing words, and any limit on the words array. With a nested request object and no return-value documentation, the description leaves meaningful gaps an agent must guess at.

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?

The description contributes zero parameter meaning; everything useful sits in the nested schema (id = wordlist to add to, words = array with duplicates ignored, projectId = detailed project scoping rules). Because the nested schema is reasonably self-documenting, the baseline 3 applies, though the top-level 'request' wrapper itself is undocumented anywhere.

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?

The verb+resource ('Add words to wordlist') is unambiguous and the second line narrows it to an *existing* wordlist, which is real information. However, the first line is essentially a restatement of the tool name, and nothing distinguishes it from siblings like wordlist-create, wordlist-words-remove, or wordlist-update. Purpose is clear but no differentiation is offered.

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?

'existing wordlist' implies a prerequisite (the wordlist must already exist), which is a sliver of usage context. But there is no guidance on when to use this versus wordlist-create (new list) or wordlist-words-remove, no mention of what happens on duplicate or unknown words, and no error/precondition guidance.

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