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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=false, so safety is covered. The description adds genuinely useful behavior beyond the annotations: it is a partial/patch update where unspecified fields are left untouched, which is or is not obvious from a mutation tool. It stops short of what happens to existing time entries or reports when a rate or client changes.

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 sentences, no filler, with the scope of changes front-loaded ahead of the patch-semantics clarification. Every sentence carries information an agent needs.

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?

An output schema exists, so return values need not be described, and annotations plus a fully documented 5-parameter schema cover most of the surface. Left implicit are the unstated required-parameter behavior (project is the sole required arg, but the description implies any field is optional) and any side effects of moving a project to a new client.

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 each parameter (name, client, project, billable, hourly_rate) already has a descriptive string, including the flexible "Client / Project" id resolution and the hourly_rate currency rule. The description only restates the field set, adding no syntax or constraint detail beyond the schema, so the baseline of 3 applies.

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?

Names a specific verb set (rename, move, change rate/flag) against one resource (project), enumerating exactly which attributes the tool mutates. This cleanly separates it from update_client and from archive_project/unarchive_project in the sibling list.

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?

"Only the fields you pass change" tells the agent how to call it, but there is no explicit guidance on when to prefer this over siblings such as archive_project, unarchive_project, or project_totals, nor any prerequisites (e.g. needing write access or a resolvable project id).

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