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

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=false): documents name uniqueness ignoring case and surrounding spaces, that creation does not merge an existing Portfolio, that duplicate IDs or wrong subject kinds are refused, and that execution is not idempotent-after-uncertainty. This is exactly the additional behavioral context the safe-write annotations don't convey.

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?

Front-loads the core action, then packs constraints, uniqueness rules, recovery guidance, and non-effects into tightly written sentences. No filler or redundancy despite high information density.

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?

Output schema exists, so return values needn't be described. The description covers prerequisites (Account access), input constraints, edge cases (duplicates, case-insensitive uniqueness), and side-effects (creates nothing else), which is complete for a mutating create tool.

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?

With 60% schema description coverage, the description fills gaps: the combined 1–100 ID constraint across clientIds/siteIds/topicIds, the refusal of duplicate IDs, and the semantic difference that a Client pulls in all its brand Sites while topics need explicit attachment. The schema already documents the individual ID arrays, so this adds cross-parameter meaning rather than syntax.

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 (Create) and resource (agency Account Portfolio) plus the distinguishing scope: name, description, and initial Client/Site/topic membership. It is clearly separable from siblings like create_client, create_site, create_topic, and update_portfolio, and it explicitly says it 'Creates no Client, Site, topic or Scan.'

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?

Gives concrete context: requires Account access, references the sibling list tools (list_clients, list_sites_and_topics) as ID sources, and instructs to inspect list_portfolios/get_portfolio after an uncertain result before retrying. It does not explicitly route modification requests to update_portfolio, so it stops short of full when-not/alternative coverage.

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