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

Annotations only declare it is not read-only and not destructive, so the description carries most of the burden. It usefully discloses partial-success semantics ('returns the keywords that were skipped and why'), but says nothing about permissions, the 10-item cap being enforced, or duplicate/write-failure behavior.

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 tight sentences, front-loaded with the action and its effect, followed by the return behavior. Nothing is wasted; only the omission of the key term mapping ('keywords' vs the schema's 'phrases') hurts.

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 write tool with no annotations covering specifics, no output schema, and 0% parameter coverage, the description is thin. It never mentions the 10-phrase limit, the required project/site scoping, or what a successful add returns, leaving meaningful gaps for an agent to fill by guesswork.

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 0% across 4 parameters, so the description must compensate and largely does not. It clarifies only scheduledDate ('optionally on a given date') and leaves projectId, siteId, and especially the phrases array (max 10 items, which it calls 'keywords' without connecting the terms) undocumented beyond the schema types.

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?

Clear verb+resource ('add keywords') plus the crucial qualifier that they are added 'as article briefs' to the content plan, which tells the agent what actually gets created. It does not, however, differentiate itself from near-identical siblings like import_article_keywords or add_outreach_keywords, leaving the agent to guess which adder is correct.

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?

The only usage hint is the optional date, implying scheduling context. There is no statement of when to use this versus import_article_keywords (bulk import) or add_outreach_keywords, which is exactly the ambiguity an agent faces with this sibling set.

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