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

Annotations declare readOnlyHint=false, idempotentHint=false, destructiveHint=false, openWorldHint=false, so the safety profile is already covered. The description adds a useful constraint (target_amount must be > 0 and <= parent goal's target), which is behavioral context beyond annotations. However, it doesn't say whether partial updates replace or merge values, or whether missing fields are left unchanged.

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?

Well-structured with explicit Args and Returns sections, front-loaded with the core action. Slightly verbose for a simple update but every line is relevant. The triple-quoted formatting is a bit rough but content is not padded.

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 4-param mutation tool with no output schema and 0% schema description coverage, the description covers the basics but leaves gaps: no return value detail beyond 'Updated milestone details', no merge/replace semantics, no error conditions for target_amount exceeding parent. Annotations carry safety, but behavioral completeness is only adequate.

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%, so the description must compensate. It does list each parameter and provides a constraint for target_amount, which adds meaning. But name and celebration_message get only 'optional' with no constraints, and milestone_id gets no format hints. Baseline is 3 given the partial compensation for low coverage.

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 (update) and resource (milestone), and enumerates the mutable fields. It does not differentiate from sibling tools like create_milestone or delete_milestone, but the verb+resource alone makes the operation type clear.

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?

No when-to-use guidance, no prerequisites, no mention of alternatives. The only hint is that fields are optional, which tells an agent it can do partial updates, but there is no explicit routing to update_goal or create_milestone for related needs.

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