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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false and openWorldHint=false, yet the description adds genuinely new behavior: partial-failure semantics where unresolvable ids are silently dropped instead of failing the call, org-scoping of accepted ids, and the return shape `{ added }`. It stops short of covering invalid portfolioId handling or auth prerequisites, so it is strong but not exhaustive.

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 action, then the return/error semantics, then the cost profile. No filler and nothing repeated from the schema or annotations.

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?

There is no output schema, and the description compensates by naming the return payload `{ added }`. Combined with the silently-dropped-id rule and the free/no-credits note, an agent has enough to call this correctly and interpret the result.

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 coverage is 100%, so the baseline is 3; the description earns above baseline by adding a semantic constraint on projectIds that the schema does not express — only ids resolving to a project in the caller's organization are accepted, and the rest are silently dropped. It does not restate the array bounds or ID format the schema already covers.

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 ("Adds projects to a portfolio") and distinguishes itself from the sibling pair create_portfolio and remove_portfolio_projects. An agent can identify the operation without opening the schema.

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?

Usage is implied by the verb but there is no explicit when-to-use guidance and no named alternative (e.g. remove_portfolio_projects, create_portfolio). The cost note ("no credits are spent") is decision-relevant context, but it describes the operation rather than routing the agent between tools.

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