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

Beyond the annotations (readOnly, idempotent, non-destructive) the description explains the token model ('compressed, not encrypted; nothing is stored') and the rebuild behavior ('Rebuilds every line'), which reconciles the apparent mutation wording with readOnlyHint=true. It also discloses output contents and a limitation ('No prices'), all of which the annotations cannot 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?

Purpose and supported operations are front-loaded, followed by return contents, the storage model, and a scope caveat ('No prices'). The sentences are dense but each earns its place; the opening sentence is long yet functional.

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?

With an output schema present, return values need not be spelled out, and annotations cover the safety profile; the description still adds the token-not-stored model and rebuild semantics. Given the tool's complexity, the definition is close to complete, leaving only explicit alternative-routing unaddressed.

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% and the operations enum is documented in detail, so the schema already carries the parameter meaning. The description's list of change types loosely maps to the operations array but adds no syntax or format detail beyond what the schema provides, matching the baseline 3.

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 description gives a specific verb and resource ('Changes a My Project project carried in a state token') and then enumerates the concrete mutation kinds it supports (rooms, dimensions, takeoffs, roof pitch, rename). It is clearly distinct from the create_project_file_* siblings because it operates on an existing token rather than building a new file, though it never names a sibling explicitly.

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?

It implies usage by stating the token's origin ('from a project file answer or an earlier update'), which tells the agent it needs a token in hand first. However, there is no explicit when-to-use/when-not guidance and no routing to an alternative tool for a similar task, so usage is inferred rather than stated.

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