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

Annotations already declare a non-destructive, closed-world write. The description adds behavior annotations can't: the line is routed to whichever block holds the given date, and re-reviewing the same week or session REPLACES the existing line (idempotency). It also states no card is created and it saves on return. It stops short of saying what happens if no block exists on that date.

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-loaded with the action and the write target, then conditions, then parameter notes. Dense but purposeful; there is mild redundancy between the list of review types and the later `date` explanation, and the nested parentheses make it harder to parse than it needs to be.

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 3-parameter mutation with no output schema, the definition covers trigger conditions, what to write, formatting, date resolution, replacement semantics, and persistence ('Saves on return, no card'). An agent has everything needed to invoke it correctly or correctly decline to.

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 already 100%, so baseline is 3, but the description adds real semantics: it ties `date` to the block resolution rule, explains what each `from` value implies, and specifies the expected shape of `text` with a concrete example (number against the goal, athlete's language, no bracketed scales).

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?

Specific verb and resource: 'Add one line to a training block's PROGRESS — under the block's GOAL on its card in Blocks.' The scope constraint (one line, attached to a goal, on a Blocks card) separates it from the sibling bulk setters like set_training_blocks and from the other 'add_' tools.

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?

Names the triggering situations explicitly (end of a Review week, Analyze on a session, a block review) and the condition that qualifies content (the reviewed thing moved/held/missed a goal metric). It also gives an explicit exclusion: 'Nothing that bears on the goal → write nothing.'

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